Hammerheads weren't enough

Published April 23, 2026

This story is shared in the hope that you can learn from it, and become a better, safer diver. The details below are accurate to the best of my memory. 

Recently I was on ecotourism cruise abroad with my family. Mostly, this trip was not for diving. It was about quality family time in nature. But, I had planned in advance to leave our main ship, and meet up with a local dive operator and get some diving in during two of the days in our cruise itinerary. I had been looking forward to this trip for months. I dive in Puget Sound regularly - but to get to dive while traveling is a treat. The local area was known for close encounters with seal lions, sea turtles, rays and a healthy population of hammerhead sharks!

The first day of diving arrived. Four of us disembarked our cruise on a Zodiac (a type of smaller rigid inflatable boat) to meet up with the local dive operator. They weren't far away, and we promptly hopped off the Zodiac onto the dive boat. Another group of six divers getting ready on the boat. We crowded in, took our seats, and were asked to fill out liability paperwork while our gear was prepped by the crew and we listened to the dive briefing. 

I was feeling a bit overwhelmed. I'm a reasonably experienced diver, but most of my diving is from shore and on my own schedule. The boat was very full of gear (BCs and cylinders were in a large pile at one end of the boat), people, and multiple things were going on at once. We struggled to pay attention to the dive briefing while also trying to don our exposure suits, stow our dry land belongings, stay out of the way of the first group, and sort out our dive kit. 

As the crew handed out our assigned cylinders and rental BCs it became apparent that the DIN nitrox cylinders I had ordered were not there. I was given yoke cylinders filled with air. The crew helped locate a DIN to yoke converter and I decided to continue to the dive on air. The crew promised the dive was shallow and didn't require nitrox. I had asked for nitrox out of conservatism (not because I was going to be pushing the limits of no decompression time). I was in a remote area and wanted to do everything I could to minimize my risk of getting bent - or experiencing even mild gas narcosis. I preferred nitrox but didn't need it for these dives. 

Often when you board a boat the crew will brief everyone on emergency and safety procedures - the location of lifejackets, where to find oxygen should it be needed as first aid, and so on. We did not receive this briefing. Probably this briefing was given before we came aboard. 

The crew did, however, brief the dive. They shared our planned max depth, the overall route, and told us the gas pressures they wanted us to watch for and communicate so that no one would run out. Buddy separation procedures were not discussed. 

The crew explained that we would dive in two groups. Those already aboard were the first group. Those of us who had come from the cruise ship would be in the second group. I watched as the crew prepped the first group. I noticed with a bit of unease that they turned each diver's tank valve fully on - and then turned it back a quarter turn.  The first group was ready. The divemaster asked them to make sure their air was on. The divers did a quick push of their purge valve or took a breath and after confirming their air was on, rolled off the high edge of the boat backwards into the sea.

It was our turn now. The crew helped us kit up on the seats. They asked how much weight we needed - or guessed for those of use who hadn't dove in similar exposure suits - and they handed out weight belts accordingly. The rental BC was unfamiliar to me and lacking the D-rings I would normally use to secure my camera, flashlight, and DSMB. I improvised but was the last one to get ready as I got myself situated and also went through most, but not all, of my usual pre-dive checklist to make sure that my equipment was all present, and my gas was functioning for proper breathing and buoyancy control.  I noticed my fill was several hundred PSI below full and mentioned it - the crew said not to worry about it. I didn't even attempt to check my buddy's kit - he was an experienced instructor - and rightly or wrongly I was not too worried about him. Everyone else was waiting for me so I focused on finishing up and getting myself ready. 

We backrolled into the water and the divemaster called for us to immediately descend. No in-water weight check I guess. OK - let's dive! 

Underwater, I began to relax a bit. The sea lions and local fish did not dissapoint. Three of us formed an impromptu, fairly cohesive team and checked periodically on each others whereabouts and gas remaining. My two buddies were a married couple with a couple hundred dives each under their betls.  They usually dove in better visibility, warmer water, and less current but they seemed in control of their buoyancy, aware of their surroundings, each other, me,  and their remaining gas. I felt lucky to dive with them.

My nominal dive buddy - a fellow instructor - was enjoying a break from having to teach class. He did not look up much from his camera, and we did not dive as a team. He was on his own. 

As the dive progressed, I signaled I'd reached ascent pressure - I had to swim to the divemaster and tug her fin to get her attention after a couple minutes of hoping she'd look my way. She inflated a DSMB, and initiated our ascent and safety stop as a group. The ascent went smoothly. 

After the first dive, the crew quickly and efficiently changed over tanks, and we motored a bit to our second dive site. In between dives there was no debrief to discuss how the first dive went. The second dive went similarly to the first - easier since the gear and boat procedures were now familiar, harder because the current had picked up and we had to fin hard at times to stay with our guide. Again I had a fill that was several hundred PSI below full - and again my gas consumption limited the team. 

While we waited for the second dive, our group chatted with a young lady who had been diving with the hammerheads  the day before. It was at the same site we were scheduled to visit on our second day.

She showed us beautiful video on her phone of schools of sharks swimming in the deep. She had had a great time.  It looked like the dive of a lifetime. I also noticed she also had some light cuts on her hand. I asked her about this and she explained that the current was so strong you have to hang onto the rocks to not drift away. She only had one glove, so she got cut by the rocks on her gloveless hand. At some point during her dive the prior day she was not able to stay in position against the current - and drifted away from the group. Her buddy and boyfriend noticed and the two of them stayed together and ended the dive. By her account she ended the dive more than 100 meters away from the dive boat. Another boat spotted them and let her dive boat know where to pick her up. Did she have a signalling device (SMB, DSMB, or emergency personal locator beacon) to make it easier to spot her in the open ocean? No. She did not have one, and the boat did not issue any signalling devices to its guests on her dive our ours. 

Decades ago this used to be considered a best practice to prevent valves from sticking open. In recent years, research from DAN and others has shown this practice has been associated with some near accidents and at least one fatality. The problem comes if you accidentally turn a valve off instead of on - and then turn it back on a quarter turn (thinking you have turned it almost all the way on). The valve may still deliver some air since it is partially open - but it may not be open enough to deliver the air you need at depth. An astute diver might just reach over their shoulder, check the valve and turn it on. Other divers may panic or simply run out of gas.