Out of Air at 85fsw
A multiday high-tempo mission was underway in an area known for warm clear water, but also ephemeral currents which can be quite strong at times. A four person team made a dive to ~85fsw to conduct a biological survey. The current had come up but the divers and Divemasters thought the dive could be made safely.
At the end of the dive, the four divers assembled on the bottom to collect their gear and reel up their survey tapes. One diver noticed they were very low on air and signaled the closest diver. The second diver immediately passed over their primary regulator and started breathing from their alternate air source. The other two divers were alerted and all four began a controlled ascent.
On the way up, the air donor was switched to another diver who had more gas in their cylinder than the original donor and also a traditional octopus second stage with a long hose. The divers felt comfortable enough and had sufficient gas to make a 3 minute safety stop at ~20fsw before completing their ascent. They were safely recovered by the dive support vessel.
- Gas consumption in high current goes up considerably and it is imperative to frequently check your SPG. It is easy to become complacent when repeating the same operations over and over again, particularly when the sea conditions are pleasant. In this case, good training proved its value as the dive buddies were maintaining effective contact, no one panicked, and the air sharing was conducted very well, but this should never have happened. • Maintain your situational awareness, know how much gas you have and how much you will need to complete the dive, know how much gas your buddy has.
- Plan for contingencies – if the current comes up, know your consumption will increase and cut the number of transect surveys from three to two. No data is worth your life and you can always refill your tank on the boat and collect the rest of the data on the next dive. • If the current is high, do not fight it. Plan a drift ascent with the support vessel in liveboat mode.
- Carry a surface marker buoy so the boat can easily find you if you come up downcurrent.
- Take a RASS with you. If all else fails you can safely ascend from any approved depth on the contents of the RASS bottle.
- Lastly, a safety stop is just that: it is for an additional margin of safety, it is not a decompression stop. In an emergency situation, ascend directly to the surface and do not make a safety stop.