Seeking Input on Low Air - No Air Situation

[tt5five]

Without bashing me too hard, I would like to get some comments on an incident on my last trip family dive trip as education for future trips. Here is the situation:
I had a low air/out of air experience during a dive to a ship wreck at 60 feet and had to use the guides extra reg to make it back up. 16yo son also had a low air situation and was sent up without safety stop by assistant guide. 16yo finished with about 50. Long story but dive group went down, heavy current moved boat, anchor was not near wreck and had to resurface, take off equipment, reposition boat, re-enter and do second decent. Visibility was 40 or less, rough sea, water colder than prior day with current. Wreck was long, and we began to report our air readings as we were making our way along the wreck and away from the anchor line. We were already getting a little concerned, which could have upped our air usage. Guide continued to end of wreck and when we turned to return to anchor line where fighting strong current. Were instructed not to surface but to get back to anchor line. Seeing my low air, I used guide’s extra reg part of the way to anchor and then tried to finish with my air. As going up, I got to almost 0 and then went back to guide’s extra reg so I could complete the safety stop. 16yo son also low on air. He was buddied with guide, but obviously I was using his buddy's air. A young female who was probably a DM in training sent the 16yo up without safety stop. I could not see what was going on because of being teathered to the main DM using his spair reg. My 14yo was my buddy and was also low on air so I could not breath off him. All our prior dives had been shallow reef dives of 35ft or less. We told the dive guide and even joked that we were newer divers and had "air hog" problems. So, I feel the DM was well informed of this being a new experience. I do know there were some times I kicked too hard and can do more to extend my bottom time. Just trying to get some feedback. 14yo and I dove the second sight that day and went back down to 50 and had a great time. I am still not sure if there was an issue or on our part or the guide(DM) or it was just one of those situations you have to work through, so looking for insight or wisdon. Always trying to learn.

 

[Cave Diver]

My first comment centers on this:

Wreck was long, and we began to report our air readings as we were making our way along the wreck and away from the anchor line. We were already getting a little concerned, which could have upped our air usage.

While this may have been a guided dive, fighting current at the end of a dive is a problem. The guide should have led you into the current during the first part of the dive when you were fresh and had the most air and then you could have drifted back to the anchor line once you hit your turn pressure on air. If the anchor was positioned in a way that it was always upcurrent, the next option would have been finding the lee side of wreck to shelter in during your return to the anchor. Yet another choice is to thumb the dive earlier and leave a larger reserve to get back with.

Even if you have a guide, the person most responsible for your own safety and planning is you.

Glad everything turned out well, this could easily have been a lot more serious.

 

[Crush]

If I was the dive buddy and parent of a 14 yo I would have had a detailed dive plan worked out with my kid, regardless of whether you were briefed by a DM or not. Did you discuss maximum depths and turn pressure? Sounds like you didn't and you really should have. Are your kids allowed to go to 60 feet at their cert level? I am unclear as to what role the current played - turn pressure and Max depth are independent of current. Presumably you went against the current when beginning the dive so that you would use less air when returning.

 

[Kenny13]

If I was the dive buddy and parent of a 14 yo I would have had a detailed dive plan worked out with my kid, regardless of whether you were briefed by a DM or not. Did you discuss maximum depths and turn pressure? Sounds like you didn't and you really should have. Are your kids allowed to go to 60 feet at their cert level? I am unclear as to what role the current played - turn pressure and Max depth are independent of current. Presumably you went against the current when beginning the dive so that you would use less air when returning.

The original post says they were fighting the current as they tried to return to the anchor line at the end of the dive. That was a big red flag for me. I am wondering about the dive planning though.

 

[Bubbletrubble]

Please read NWGratefulDiver's essay on gas planning and management.

The diver and his/her buddy, not the DM/guide, are ultimately responsible for monitoring the buddy team's gas supply. Understand that your buddy is carrying your emergency reserve gas and vice versa.

Cave Diver makes some very good points regarding wrecks and current.

This is really an issue of inadequate or nonexistent gas planning/management combined with following a DM and trusting that he/she will ensure that you are safe -- instead of being assertive and taking control of your dive. If you were taught to surface with at least 500 psi in your tank, at what pressure must you start your ascent from 60 fsw to ensure that you end up with 500 psi at the surface? Don't feel bad if you don't know the answer to this question. Most basic OW students aren't taught how to figure this out.

If you or your dive buddy reach the turn pressure (agreed upon in pre-dive planning), then you turn the dive. Simple as that. Inform the DM/guide as a courtesy if it's convenient. Then follow your ascent rate and stop schedule that you agreed upon in pre-dive planning. Pay attention to any surface hazards (boat traffic?) that the DM/guide informed the group of in the pre-dive briefing.

FYI, although a safety stop is considered good diving practice, it is not necessary.
In an OOA situation, the priority is ensuring that the OOA diver has a reliable gas supply.
The most reliable gas supply is at the surface.

On a side note, it's best to share air with a buddy before the situation transitions from a low-on-air (LOA) to out-of-air (OOA) situation. This is a good idea because it allows the LOA diver to keep a little gas in his own tank. It gives him the option of switching back to his own gas in case the buddy pair get separated during the shared-air ascent (yeah, this happens). It also gives him another option to establish positive buoyancy at the surface, via power inflation of the BCD.

 

[vinegarbiscuit]

Agreed that that swimming into the current on the outward leg is the best way to tackle such a dive, or to use the wreck itself as shelter from the current. In such situations, it's highly desirable to make it back to the anchor line, since doing a free ascent in a strong current can put you a considerable distance from the boat. It's not always easy for the boat to immediately pick up drifting divers in such circs, since the captain may have divers completing safety stops/deco/whatever on the line. That can only happen after all the divers are back on the boat, and by that time, the drifters may be very far away and not easy to spot. Long story short - that's why it's critical to plan for sufficient gas to make it back to the anchor line and perform safety stops (although, as a no decompression dive, safety stops are highly recommended, not compulsory...something to bear in mind in an excrement-hit-the-extrusion-device situation).

You did great to brief the guides about your status as new divers and high air consumption. Based on your knowledge of your air consumption, consider planning future dives (with your buddy and guide, if you use one) to turn the dive at an agreed-upon pressure, so that you are both back at the anchor line with enough gas in your tank to get you and your buddy to safety. Your turn pressure - and the quantity of air in your tank as you begin your ascent - will be determined by a myriad of factors, such as breathing rate, water depth and tank size. It's known as 'rock-bottom' dive planning...there are numerous excellent post on the topic on SB, as well as the internet.

 

[tt5five]

Thanks for the input. Good points. (I'll respond to both comments at once.) Crush - What is turn pressure? The 14yo was in the best shape on this deal. (We are certified OW and took a long, multi-week course with lots of pool time. I was glad no one paniced and did anything stupid. Took the long course with the kids for just this reason.) I just did not want to use his (14yo) aire and then put him in the same situation as me and the 16yo. The dive plan was to decend to 60, go to the end of the ship and return to the anchor line. I guess where it derailed was when we were still going with the current, gave our our pressure and signaled to go up because we were at the 800 mark (where our DM trained us to go up), and the DM motioned us to continue to follow. From comments above, probably should have left DM and gone back to anchor line - that is what I am getting out of comments. Going with current on first leg was also probably somehing that was not a good idea by DM. I will check direction from now on. Thanks.

 

[Cave Diver]

Thanks for the input. Good points. (I'll respond to both comments at once.) Crush - What is turn pressure?

Turn pressure is the pressure at which you decide it's time to turn the dive and return to your exit point. When diving under certain conditions, you need to be more conservative with this pressure, because as you found out, it may take considerably more to exit.

It is best to have some idea of this pressure discussed in your pre-dive plan. However you may find the need to adjust it to the conditions you find once you get into the water.

 

[rubixcube]

What is turn pressure?

It sounds like a difficult and poorly planned dive (poor conditions, fighting current on way back, lack of real planning in general), I think that reading over that article and making an effort to plan thoroughly will help with some of the problems.

 

[Cave Diver]

Turn pressure is the PSI/BAR at which the diving pair/group begin their ascent.

I would correct this slightly to say that it's the pressure at which you turn your dive to return to your exit point. The amount of air needed to ascend can be considerably less than your turn pressure.