Know your gear

Steel and aluminum are common cylinder materials. In the US steel tanks have rounded bottoms whereas aluminum tanks are flat-bottomed. 

Steel tanks usually sink more (they are more negatively buoyant) than comparably sized aluminum tanks. This makes them popular with cold water divers, who don't have to wear as much lead when using a steel tank. Aluminum tanks are common in warm locations and as additional tanks for tec diving or as a backup gas supply because they are closer to neutrally buoyant. 

Check the shoulder markings (and bottom) for the capacity and service (fill) pressure in PSI or bar. 1 bar = 14.5 PSI  https://www.xsscuba.com/cylinder-markings . Tanks and pressure gauges in the US are usually rated in PSI.

Service pressures range from low pressure (LP) of ~2,400-2,640 PSI, to standard of ~3,000 PSI, to high pressure (HP) of ~3,500.  The most common aluminum tank, an 80 cubic foot capacity tank, is usually 3,000 PSI. HP steel cylinders are often 3,442 PSI. 

Note the capacity, often marked on the shoulder. In the US it is customary to express capacity in cubic feet of gas. 80 cubic foot aluminum tanks are the most common. During your dives, log the capacity of your tank, your starting and ending pressure, and your average depth (logged by your dive computer). This will allow you to calculate your gas consumption rate. About 0.5 cubic feet (at the surface) is typical for an adult male at rest. Knowing your consumption rate, you can calculate if the tank you've chosen for your dive has enough gas to complete your dive as planned.

Verify the tank has been hydrostatically tested, "hydro'd",  within the last 5 years. Hydro dates are stamped into the metal on the shoulder of the tank. For example:  03/21 would indicate a hydro test in March of 2021. Month and date will be separated by a special mark of the tester. Find the most recent date stamp. Don't use tanks with expired hydros.

Verify the tank has been visually inspected or"VIP'd" within the last year. The VIP checks for cracks, corrosion, and a functioning valve seal. This is indicated by a sticker, usually punched on the month, year, and date of inspection. Do not use it if it is out of date.

Check for any obvious signs of damage (giant dents, big rusty scratches, mangled valve threads, bent valve, etc.). Don't use if you suspect the tank or valve may no longer be structurally sound.

Check the tank markings to verify the gas mix. Most tanks without special markings are for air. A green and yellow VIP sticker or tank bands in the US may mean the tank is used for an oxygen-enriched air, "nitrox" mixture. The visual inspection sticker may have this information. Do not dive a tank marked for nitrox unless you have been trained to do so, or it has been tested in your presence  with a calibrated oxygen analyzer and contains a normal oxygen percentage (~20.9%). NEVER dive tanks containing nitrox or pure oxygen unless you have received appropriate training.  This can be fatal. Taking them beyond their rated maximum operating depth (which may be as shallow as 20 feet for pure oxygen) can result in convulsions and death.

Smell your gas to check for contamination before every dive. Gas can become contaminated if the filling compressor is not functioning properly, if their are problems with the filters, or if the air intake is contaminated by boat or other vehicle exhaust. Turn the valve gradually and gently until it is barely open and smell the gas coming out. It should smell like nothing. Do not dive a tank with any moldy, smoky, or gasoline type odors.

Check whether your tank valve is yoke, DIN, or a hybrid "pro valve". For yoke, the o-ring sits in valve and a screw is used to clamp the valve and regulator face together. For DIN the o-ring is retained in the regulator 1st stage and the 1st stage screws directly into a threaded tank valve. Pro valves are yoke and DIN. With the "din-sert" (DIN insert) inserted, they mate with yoke regulators. Remove the DIN-sert and it exposes threads that allow it to mate with a DIN regulator. Verify your tank (yoke) or regulator (DIN) has an o-ring in good condition. 

Ask for a tank that is a good fit for your stature and strength. Here in the Pacific Northwest, steel HP 100 (high pressure 100-cubic foot) and HP 80 tanks are common. HP 80 tanks are much lighter (9 lbs of dry land savings when full compared to an Alumninum 80 or an HP 100) and are significantly shorter. They better fit people with shorter torsos and are easier to carry due to their lighter weight. Most women, adolescents, and shorter men will be more comfortable in an HP 80 than an HP 100. If you are a tall, strong person who goes through air quickly, you might also ask for a larger tank (bigger than an HP 100).

When starting and ending dives, always fully open or fully close your tank valve. A tank that is not fully open can result in an inadequate air flow at depth. An old practice was to open the valve fully then turn it back a quarter turn. Do not do that. Partially open (or partially closed) valves have contributed to several accidents and fatalities. 

Your BC uses air to adjust the volume of water you displace - which allows you to achieve neutral bouyancy - neither sinking nor floating - at all times during your dive. At the surface, before and after diving, they should always be inflated to keep you floating with your head out of the water so you can breathe easily. 

Check that your BC fits you. You should be able to adjust it to be snug, but not constricting. 

Locate all of the valves for deflating your BC and practice using them by feel / muscle memory when you dive and during your predive safety check. Know when to use which deflator. For example, since air rises in water, hip dump valves allow you to vent gas when you are horizontal or head-down in the water. 

Often, jacket-style BCs have 4 deflator mechanisms. (1) Press the button at the end of the inflator hose. (2) Pull the inflator hose to vent from the left shoulder dump. (3) Pull the string attached to the right shoulder to vent from the right shoulder. (4) Pull the string located near your hip/kidney/butt to the left or right side of the tank. 

Check that your inflator hose and valves are securely attached by twisting them clockwise to make sure they are snug. They often screw on to a fitting welded into the BC. They can come loose. If this happens during a dive, your BC may be unable to maintain sufficent air for your to establish neutral buoyancy - which can increase your risk of an uncontrollable descent, or make it hard to ascend to end your dive. 

Check that you can inflate your BC with both the power inflator (low pressure inflator hose) and the oral inflator. If it does not fit you properly, it may be difficult to reach the oral inflate mouthpiece to your mouth. Adjust or get a new BC if necessary.

Verify that your BC holds gas and does not leak when inflated. 

Check for wear and verify function of all buckles, straps, and releases.

Check the integrated weight system (if present) for your BC. Know how to secure weight so it doesn't come loose during a dive. Know how to operate the quick release so you can drop your weight if you have a problem staying buoyant at the surface. Many BCs have weight pockets that slide in and out. Verify the max weight capacity of your pockets and do not exceed it. Your BC may also have trim pockets to carry small amounts of weight. Often these are threaded onto the cylinder cam band(s) or may be built in pockets attached to the back of the BC itself. These can be used to move some of your weight around to help achieve optimal trim. 

Consider the lift capacity of your BC. The lift capacity measures how much negatively buoyant weight it can offset. You can look this up online or it may be printed on your BC. Many BCs designed for warm water diving have a fairly small lift capacity. Check that when loaded with weight, and a full tank (which is negatively buoyant) your BC can still float. If not, get a BC with a higher lift capacity or move more weight to a different sytemt (weight belt or harness). If your BC cannot float when fully inflated it can contribute to problems getting in and out of boats, or in the event of an issue that requires you to remove your scuba kit at the surface.

Consider a backplate and wing style BC. Most divers learn in jacket-style BCs, but backplate and wing configurations (BP&W) are becoming more popular with recreational divers. This BC style is standard if you progress to tec diving. Typically, a steel or aluminum backplate and nylon webbing harness form the structure of a BP&W. An air bladder called a "wing" is screwed on to the back of the backplate. The wing will have a standard BC inflator hose.  BP&W style BCs move some weight onto your back (in the form of the metal plate) which puts it near your center of gravity and distributed nicely between shoulders and your lower back. This can make them more comfortable and stable - particularly in cold water where we carry a lot of weight. BP&Ws locate your air bladder above you when you are swimming - which makes it easy to stay in horizontal trim (but a bit harder to stay vertical at the surface). BP&W systems are modular. If a component fails you can switch out the broken bit and keep diving instead of having to replace your entire BC. They are customizable - so you can move your D-rings and other components to where you need them. Many experienced divers choose to carry a redundant air supply for deeper dives. It is easier to carry such a "pony bottle" (clipped to the left chest and hip D-rings) with a backplate and wing than it is with many jacket-style BCs.

Service your BC inflator mechanism annually or as recommended by the manufacturer or earlier if it begins to leak or stick open or closed. Often, replacing the inflator is easier and less expensive than servicing it. An inflator valve that sticks open can suddenly and rapidly fully inflate your BC leading to a dangerous uncontrolled, buoyant ascent. In a pool or shallow water, practice disconnecting your BC inflator hose while swimming down and dumping air from a hip dump valve in case you ever have to respond to this problem on a dive. 

Consider a bright color especially if you dive in low-visibility water like we do here in the Pacific Northwest. 

The 1st stage regulator reduces tank "high pressure" to an intermediate "low" pressure of ~125-150 PSI. This is  delivered via low-pressure (usually labeled "LP") ports in the regulator to the hoses for 2nd stages and BC/drysuit inflators. It also has tiny holes in the "high-pressure" (HP) ports that allow tank pressure to pass directly to your SPG or air-integrated (AI) transmitter so you can track remaining tank pressure.  

Consider a DIN regulator. If purchasing your own regulator for local use, you may prefer DIN. Because of the o-ring placement and deep, threaded connection between the valves themselves, they are not prone to blowing out an o-ring which can lead to rapid gas loss on a yoke regulator. DIN is considered a safer and more secure connection. DIN regulators are required if you progress to tec diving. DIN regulators can use an adaptor to connect to a yoke tank, but the reverse is not true. 

Consider the regulator's rated operating temperature. Many regulators designed for warm-water are only rated for temperatures above 50 degrees Farenheit (50 F / 10 C) and the manufacturer states not to use them below that temperature due to an increased risk of a free flow. If you will be diving here locally, our water is frequently colder than 50 F. An environmentally-sealed regulator rated for colder temperatures may reduce your risk of a free flow. 

Fasten your first stage to the tank valve finger-tight only. Don't tighten with your fist or it will be hard to remove.

Check your for an o-ring. Replace it if it is worn or leaks air when connected. The o-ring is in your regulator 1st stage (DIN) or tank valve (yoke).

Check that the 1st stage filter (looks like a metal sponge) is clean and free of any significant corrosion or debris.

Check that the dustcap is present and secured when the regulator is not in use. If needed, dry the dustcap before re-attaching it to the regulator to avoid introducting moisture into your regulator.

Service your regulator acccording to manufacturer instructions. Most regulators are serviced annually or every two years, or more often with heavy use or any time they malfunction. 

Inspect mouthpiece:  Ensure cable tie is present and secure. Check for rips in mouthpiece, replace if needed.  An unsecured or damaged mouthpiece can lead to breathing water instead of air. 

Negative pressure test: breathe out through the mouthpiece (to clear dust/sand), then breathe in to check for leaks in the exhaust valves. Do this  withthe  dust cap in place. Leaking exhaust valves can lead to your regulator breathing "wet". 

Check for effort of breathing. It should breathe easily when you inhale and exhale. Some regulators are adjustable. If it hard to breathe, have it serviced before diving it.

Check for freeflow. The regulator should not leak air when you are not inhaling. 

Check the hose condition. It should have no significant nicks, cuts, cracks, signs of aging, corrosion at crimp, or leaks. 

Replace hoses every 5 years or if they show signifcant signs of wear to prevent failures which could lead to loss of breathing gas at depth. 

Check underwater for leaks (bubbles) at beginning of every dive. Your buddy may be better able to spot these than you. Check each other. 

Service your regulator annually or as recommended by manufacturer.

Consider where  you will clip or stow your alternate 2nd stage or "octo".  It should be somewhere in the triangle formed by your chin and outer edges of your ribs. 

Consider a primary-donate, long-hose configuration.  This gear configuration gives you seven feet instead of three feet of hose for sharing air. This makes sharing air more comfortable by allowing you and your buddy to spread out a bit instead of having to be in each other's face. It may also make it less likely that you accidentally dislodge the regulator from your buddy's mouth in an air-sharing emergency.  Panicked out-of-air divers are reported to often grab your primary regulator anyway - if this happens, this gear configuration keeps your alternate backup regulator where you can always easily retrieve it, just below your chin on your necklace. This configuration is typically required for tec diving.

To connect the quick disconnect (QD) fitting - push the hose onto the male valve fitting while pulling the female flange of the fitting backwards toward the 1st stage end of the hose. The same process will allow you to disconnect: push the hose into the fitting while pulling the flange away from the fitting, then pull the hose off the fitting once you feel it disconnect. Connecting and disconnecting is easier when there is no pressure in the line. If the line is pressurized, pushing the inflator button while disconnecting may help relieve the pressure so you can disconnect more easily. 

Check if the metal valve connection is easy or difficult. If the valve stem or the hose end of the quick disconnect are soiled or worn, they may need to be cleaned or replaced. 

Practice disconnecting quickly by feel, while swimming down and venting from your hip dump and then using the oral inflate mechanism to re-establish neutral buoyance. This is the procedure to deal with an inflator that sticks open (on) which could lead to uncontrolled buoyant ascent if you don't vent the excess gas and disconnect the inflator hose. 

Check the hose condition for significant nicks, cuts, cracks, or signs of wear and replace if damaged.

Replace the hose every 5 years even if no signs of wear are evident to avoid hose failure and sudden loss of gas at depth. 

Check that the gauge reads reads 0 PSI or 0 bar when not pressurized. If it does not, replace it. Do not dive it. 

When turning on your tank valve, point the plastic or glass gauge face away from others (against your tank or the ground is a good practice) in case the gauge mechanism breaks and causes the gauge face to shatter/break (very rare). 

Verify tank pressure is full or nearly full before diving. It should roughly match your service pressure. Avoid overfilling your tanks which can lead to premature metal fatigue.

As part of pre-dive safety check, test breathe your 2nd stage regulators while watching the pressure on your gauge or air-integrated computer to verify air is flowing without restriction and tank valve is fully on. The pressure should drop minimally or not at all when you breathe.

Consider where you will clip or stow SPG so it does not dangle

Replace your SPG high-pressure hose every 5 years  or if it shows significant signs of wear such as deep nicks, cuts, scratches or cracking. 

Consider an air-integrated pressure transmitter (and computer to receive the signal) if buying your own gear. AI systems allow you track your gas pressure on your computer instead of requiring an SPG and hose. Transmitters may be more reliable than analog pressure gauges and may allow you to eliminate a hose from your kit increasing streamlining and decreasing failure points. Divers who use their computer to monitor all their limits (e.g. depth, time, gas remaining, no deco time) may be more likely to notice when they are approaching a limit - than if they have to remember to check separate gauges for remaining gas pressure.

Verify it turns on and the battery level is sufficient to complete the dive. If it indicates low battery then replace or charge the battery before diving.

Verify all buttons operate smoothly.  Computer buttons can stick or become non-functional if clogged with sand, silt, or salt. If needed, clean your computer button mechanisms out before diving so they work properly. You can do this with a gentle blast of compressed air or a warm water rinse.  

Set it to the correct gas. If you are diving air it should indicate "air" or "21%" FO2 (fraction oxygen) depending on the manufacturer. If you are diving enriched air (Nitrox) set it to the appropriate oxygen percentage that you have analyzed from your tank (e.g. 32% or 36%). 

Set the correct time and date. This lets you track the time of day underwater (e.g. if the captain orders to "return to the boat by 11 am!") and also aids in accurately logging your dives.  

Read the manual before diving it. In particular, learn how to read depth, dive time, no decompression time remaining (often "no deco" or "NDL" - no decompression limit), emergency decompression stop instructions, safety stop instructions, maximum operating depth alarm (MOD) if equipped and if you diving nitrox. 

Set your computer to match your intended dive plan and check limits for accuracy. Consider adjusting safety stop duration (many allow you to set for 5 minutes for more conservatism), setting a max depth alarm, a low deco alarm, or other custom alerts if supported by your computer. 

When purchasing, consider the type of diving you intend to do - do you need a multigas computer? Almost all computers will calculate nitrox and air dives on a single tank. If you have trouble with close vision, consider screen size and font size. Will  the computer you dive be the same as your buddies? If not, be sure to familiarize yourself with each other's computers. Is it rechargeable or easy to change the battery? How customizable is the computer? Can it alert you to issues (e.g. exceed planned depth) visually, with beeps, and/or via vibration? Does it come with a compass?

Air integration (AI) is an increasingly common feature that allows you to track your tank pressure on your computer. AI computers can usually estimate gas time remaining based on your consumption rate, remaining pressure, and depth. Diving with an AI computer may allow you to dive without an analog SPG and hose - increasing your streamlining. Not all computers support air integration. Air integration always requires a transmitter that is screwed into one of your 1st stage high pressure (HP) ports.

Visibility can be limited underwater, so a compass is standard dive equipment.

Verify that you have one and know how to use it before each dive. 

Verify that the card spins freely and points to north when the compass is held horizontally. . 

Most analog compasses have a card (the circular bit that rotates to point toward magnetic north) that glows in the dark if you shine your light on it. This is useful in low light conditions and at night. 

Many computers and even some underwater cameras (e.g. the Olympus TG-5, TG-6) have built-in electronic compasses. You may choose to use these instead of an analog version or as a backup. They may require calibration to work properly - especially after battery changes. 

Consider whether you like a console mounted or wrist-mounted compass.

Know that a compass will point to magnetic north. This will not perfectly match true/geographic north. In our Seattle area the magnetic declination between magnetic and true north is about 15 degrees - not small! So if you are orienting to a dive site based on a map that uses geographic north (e.g. Google or Apple Maps)  - note the difference (the magnetic declination) and adjust your dive plan accordingly. 

Consider which weight system(s) are appropriate for your dive. When cold water diving in a thick wetsuit or drysuit we often have to carry 20-30 or more pounds of lead. For your safety, this is best distributed between two or more weight systems - such as a the weight pockets of your BC and a weight harness or belt. If you instead put all of the weight in your BC - it may not be able to float (even when fully inflated!) which presents additional risks to you if you need to get in or out of your kit in water too deep to stand. 

Weight integrated BC - check the weight capacity of your pockets, don't exceed that amount, and know how to secure and release your pockets. 

Trim weights - these are often pockets built into your BC or threaded onto your cyclinder band(s). These should be used for small amounts of weight that help you adjust your trim to be horizontal in the water (e.g. if your head tends to float - you can move some weight toward your head to compensate). 

Weight belt - weight belts are one of the oldest methods of carrying weight and they haven't changed much in decades. You can get traditional styles where the belt threads through each hard weight, or a belt with pockets that can hold hard or soft (filled with lead shot) weights. Ensure it is long enough for your waist size and can be secured snugly. Weight belts have a nasty tendency to fall off if not snug - especially on individuals whose hips are not wider than their waist. Losing a belt at depth can lead to an uncontrolled ascent which brings us to weight harnesses. 

Weight harness - these are just belts with should straps (look like suspenders). The shoulder straps keep the weights from falling off if you are oriented vertically in the water or if your buckle should come unfastened. For this reason they may reduce your risk of uncontrolled ascents. Most weight harnesses will have a quick release system to allow you to still quickly ditch your weight should you have a surface emergency and need to establish positive buoyancy (become floaty to keep your head above water so you can breathe). 

Learn more: Weighting for cold water diving 

Perform an in-water weight check to verify you have just enough weight to be neutrally buoyant with no air in your BC at the end of your dive. Do this any time you change gear configuration (e.g. wear a different exposure suit, different tank, regulator, undergarment, change in your own body weight). See: Calculate your weighting  for step-by-step instructions. 

Consider hard (solid lead block) versus soft (lead shot) weights. Soft weights are less likely to hurt you if you drop one on your foot, but over time they tend to rip holes and need to be replaced. Also, they act like sponges and hold water - which can be a downside if you are putting all your gear in and out of your car. Soft weights can only be used in pockets. Hard weights don't absorb water - so they dry off quickly, they are nearly indestructible, and you can get plastic-coated hard weights if you are concerned about lead exposure. Hard weights usually have cuts in them to allow them to be threaded onto a weight harness, backplate and wing harness, or weight belt - and they can also fit in weight pockets.

Know that a steel or aluminum backplate along with a v-weight (which fits to your backplate) can be used to carry part of your weight. Steel backplates are often about 5 pounds negative - allowing you to take some weight out of your pockets, belt or harness. Because backplates are spread out from your low back to your shoulders many divers find this weight is easier to carry and promotes better trim than weight concentrated at your waist in a belt or BC pocket.

For recreational diving, ensure that enough of your weight can be quickly released so you can easily float and breathe at the surface in the event of a problem at the surface.

Exposure suits range, in order of increasing warmth, from just a skin suit (to protect from the sun and jellyfish stings), to shorty wetsuits, full wetsuits, double-layered wetsuits and drysuits. In our local waters temperatures are usually between the low 50s and mid 40s Farenheit - sometimes dipping into the high 30s especially at depth in lakes in winter. 

The vast majority of divers here who can afford to do so, dive in drysuits. They are much warmer than even a 2-layer 7 mm thick wetsuit so you stay comfortable in our cold conditions. Drysuits keep you warmer because they trap air between you and the water - and air is a much better insulator than water trapped inside a neoprene wetsuit.

Adding dry gloves, a third layer (e.g. fleece vest between your base layer and undergarment) and a thick (10 mm+) hood can make diving comfortable even in the coldest local conditions. Some divers even use heated vests. Use them with caution - there are special considerations so that you do not increase your risk of DCS. 

Diving a drysuit requires some training - get drysuit certified before attempting to dive with one. 

In the summer, for shorter or very active dives (staying active keeps you warmer) some divers do still choose to dive in wetsuits here. They have the advantages of being much more affordable (initial cost is lower, though cost per dive may not be), readily available, and do not require additional training. 

Some newer, higher end models of wetsuits have linings, sealed seams, and seals at the wrist and neck that make them "semi-dry" and these are quite warm compared to a standard wetsuit. 

Consider a bright color especially if you dive in low-visibility water like we do here in the Pacific Northwest. 

Service your drysuit according to the manufacturer instructions or earlier if your inflator or exhaust valves stick or leak - or if the suit itself leaks. 

Consider stainless steel spring heel straps - they are durable, easy to don and doff, and require no adjustments to stay snug. They also rarely break or fail to work. They are more expensive to start with - but should last you many years.

Fin style - consider whether they will they work well for all types of finning including frog kick, helicopter turns, and back finning. 

Locally we use open heel fins that can fit over thick wetsuit or drysuit boots. If you are going warm water diving you may also consider a closed heel fin that fits directly on your bare foot. 

Get scuba fins, do not buy fins optimized for snorkeling or freediving. 

Try your fins on with the boots you intend to use with your wetsuit or drysuit

Consider a bright color especially if you dive in low-visibility water like we do here in the Pacific Northwest. 

Appropriate fit is key. The mask should not leak if you inhale while gently holding it to your face on dry land (without a strap). Try this with a regulator or snorkel in your mouth which changes your face shape a bit and can impact the fit of the mask.

Shave your moustache or stubble to reduce leakage under the nose. A full mustache will usually leak less than 1 or 2 day old stubble. 

Consider whether you would benefit from prescription lenses, or reader inserts (kind of like bifocals for your mask) to be able to read your gauges and computer if you need to correct your vision on land with glasses or contacts.

Carrying a snorkel when you dive gives you a good option for being able to breathe while keeping your head in the water without having to consume your cylinder air. It can be a life saver during long surface swims or choppy conditions. 

Carry a SMB/DSMB (surface marke buoy or delayed surface marker buoy) or other visual signaling device on every dive.  Sometimes called signal tubes these make you much more visible at the surface and can make it easier to reunite with a boat, buddy, or to get attention in an emergency. A DSMB can also be deployed from depth - and makes a great way to track your depth and control your ascent if you do not have an anchor line or other reference to follow (a "blue water" ascent). 

Carry a whistle or other auditory signaling device on every dive. It can be used in emergencies to get attention, to alert a boat to your presence, to reunite with a buddy or boat in the dark or in fog. 

TIP: buy these items and take them with you. They are small,  relatively cheap, travel easily and frequently are not included with gear rental.

Carry lights. Here in the Puget Sound it is dark at depth, even in broad daylight due to plankton in the water column. For that reason at least one flashlight during the day (2 is better) and at least 2 if you are going night diving is standard. Many dive lights can also be used to signal SOS or get attention in the dark. Modern LED lights are often paired with rechargeable lithium ion batteries and are quite bright and have good run times. 

Carry cutting tools. You may choose to carry a razor-blade cutter, medical ("EMT") shears, and/or a traditional dive knife - but have something (2 is better!) that you can use to cut fishing line, fishing nets, or other similar items that may entangle you as a diver. You will rarely need these in most dive environments but should you need them they can save your life. Carry them where you can access them easily even if you do not have full freedom of movement. 

To the extent possible, stow gear where it is clipped away and streamlined. Attaching bolt snaps to your safety accessories can make them easy to clip to a BC D-ring or the retaining loops inside a drysuit thigh pocket. 

When you go diving - have an Emergencey Action Plan (AEP) and know where you can access emergency oxygen, first aid, emergency services, an AED and your nearest hyperbaric chamber and plan your dive accordingly!

Breathing 100% oxygen is standard first aid for many dive related injuries such as decompression sickness or an arterial gas embolism. You can buy an O2 kit for yourself and receive training on how to use it (ask your local shop), or ask if your guide, dive buddy, dive shop, dive club or instructor will provide one. 

Know how to reach emergency services. This can be as simple as making sure you hae a cell phone to call 911 if you are diving from an urban area. In remote areas consider whether you will use a marine radio, satellite phone, or other method to reach emergency services.  

AED (Automated External Defibrillator) - heart attacks are a leading cause of diver injury and death, particularly among older divers. Access to an AED may save someone's life. Know where the closest one is for your dive site. Many local dive sites have AEDs nearby at restaurants, hotels, or public facilities like ferry terminals.