What Should I have done?

[34109411]

I am an on again, off again diver with about 30 dives over a course of 25 years. Taken the full certification course twice ( PADI and SSI) and some refresher dives.

Last week in the Caribbean I was doing the second dive of my trip ( did a refresher dive for the first dive) and I was with my son and a guide. My son was doing his second discovery dive as he liked his first one so much. So three of us in the water doing a shore dive swimming out to a reef and swimming back. I was in back, son in front of me and guide leading the way. My son is very comfortable in the water and had no problems all dive. I had no problems other than my mask was ill fitting ( old mask) and it filled with water a little. We were only 40 feet down and I simply kept clearing as I went along the dive.

As we turned to head back to the shore at the midpoint of the dive the guide asked how much air I had and it was about 1800psi. I thought that seemed pretty low for just making the turn but it was warm, fish were everywhere, I was calm and the guide seemed unfazed.

As we were swimming back it got shallower and shallower and we were in about 35 feet and I checked the gauge to find I had about 700psi. We were still a decent ways from shore and I started to think about what I do when I take a breath and no air in the tank. I figured I could simple do an ascent if needed so all was good.


As we swam farther, the depth got to about 15 feet and I got to about 400 psi. We still had about 100 yards or so to swim and I was thinking I would definitely drain the tank. We finally got to the stopping point in about 10 feet of water and I hit the BCD to give it a shot of air and nothing. No bueno. I kicked to the top and inflated my BCD orally. My tank was on zero.

Told the guide I drained the tank and he made a cringe type of face and we then climbed the ladder out of the water. Told him I felt OK as I knew I could always surface if needed, so didn't worry about it too much.

If going by the book, should I have swam up to him when I had 800 or so PSI in the tank and showed him? Should I have surfaced with some air in the tank and surface swimmed back to the get out point?

Thoughts?

depend who you ask. Usually 750 is reserve. The DM or you should have agree of two things. First turning point of the dive, second at what pressure you go up. You usually avoid to drain completely a tank. No matter what i always finish my dives with at least 1000 psi. (1/3 rule). Better be safe than sorry.

Cheers

 

[rongoodman]

1800 psi to turn is more than enough to finish the dive with heaps left. It means you probably only used 1200 psi on the way out, so should have ended with 600 psi.

That makes me wonder if he misread the pressure at the turn and actually had less than 1800 psi remaining. The only other reason I can think of for such a disparity would be swimming into a current.

 

[Doc Harry]

1. You had plenty of gas at the turn-around point, 1800 psi. Then you had only 700 psi. Did that surprise you? If so, then you should have asked someone to check you for air leaks.

2. During the dive, the entire team should be communicating gas state to each other at regular intervals. Everyone should know everyone else's gas state. Especially when you hit 700 psi. You should have swam to the dive instructor and signaled your gas state.

3. You don't want to drain a tank to zero underwater, because sea water will reverse through your regulator and into the tank. If you're in the shallows at 15 feet and you have 200-300 psi remaining, it's time the thumb the dive.

 

[johndiver999]

1. You had plenty of gas at the turn-around point, 1800 psi. Then you had only 700 psi. Did that surprise you? If so, then you should have asked someone to check you for air leaks.

2. During the dive, the entire team should be communicating gas state to each other at regular intervals. Everyone should know everyone else's gas state. Especially when you hit 700 psi. You should have swam to the dive instructor and signaled your gas state.

3. You don't want to drain a tank to zero underwater, because sea water will reverse through your regulator and into the tank. If you're in the shallows at 15 feet and you have 200-300 psi remaining, it's time the thumb the dive.

I agree. There is a huge difference between 2-300 psi and ZERO. Assuming the spg is correct, (which is a big IF), you can ascend 30 feet and inflate the BC and relax on the surface easily with very little air - if you are calm. But running the tank to zero and swimming up and not having enough to automatically inflate the BC is something that should be avoided.

For most people, if they have one little problem, like an entanglement or dumping too much air from BC on ascent (and having a little too much lead) ascending with ZERO is really pretty dangerous and probably completely avoidable - There are very few valid reasons to run the tank to zero on a dive.

If I am deliberately running my tank down very low, I will generally test the pressure by inhaling as fast and as hard as possible. If I feel any resistance, then I know that I really must begin the ascent immediately, regardless of what the SPG says (could say 50 psi or 300). I also pretty much always have a pony bottle with me, so the consequences of running the main tank down are less urgent for me. I don't remember running a tank to zero ever, to be honest.

 

[Calmseas]

So, your son was on a DSD dive, how much air did he finish the dive with? Do you know your gas consumption? Maybe you would benefit from a larger cylinder.

My son finished with about 850. He breathers much slower than I do I guess. I have always sucked air pretty quick.

 

[Calmseas]

Outbound's comment needs to be emphasized. You should never begin an ascent by adding air to the BCD with the inflator button. You should have been able to make a lazy kick or two and begin a s l o w ascent to the surface. That last 10 feet may be the most dangerous part of the dive because it is when changes in air volume, both in your BCD and especially your lungs are the greatest. If you inflate your BCD and rocket to the surface, even in only 10 feet of water, you can create a lung overexpansion injury, even a fatal one.

I should correct that. I was at about ten feet, finned up a few times and then, after already at the surface, I went to put some air in my BC so I could relax and sit on the surface. I was not trying to put air in so I could surface

 

[Calmseas]

Thanks for all the advice. As I said, I have done about 20 dives over a 25 year period so its a rarity for me to spend much time in the water. Although, I am very comfortable in the water and don't bet panicked, just trying to figure out a way to be safe. I was never panicked and its possible the gauge was a little lower than 1800 at the turn as it was an old gauge, old gear. I was pinned to watching it as we swam in and yes it did get hard to breathe the reg and empty tank started to want to pull me towards the surface. Was having to fin pretty hard to stay down.

This was our second dive of the week as we did an orignally discovery with this son and my older son two days before. My younger son wanted to go again and my older son had an ear issue so he sat out this second dive. On the first discovery dive it was largely the same as this one. The guide in front, my two boys next to each other behind him and me bringing up the rear. The discovery dive instruction pretty much consisted of ( this his how you clear your mask.....now show me. Breathe through this thing, ......now lets go dive). On neither dive did we discuss air plans, turning, etc. Just followed the guide and told him what our air was. I surfaced with about 450 in the first discovery dive.

 

[scubadada]

My son finished with about 850. He breathers much slower than I do I guess. I have always sucked air pretty quick.

I assume you used an AL80. If you know your gas use in psI (start presssure - end pressure), your avg depth (from your computer log or download), and your dive time, you could calculate your gas consumption (cu ft/min), or we could calculate it for you. Gas consumption is very useful in planning your dives, to avoid running low or out of gas. It might help you choose your rental tank.

 

[hammet]

Thanks for all the advice. As I said, I have done about 20 dives over a 25 year period so its a rarity for me to spend much time in the water. Although, I am very comfortable in the water and don't bet panicked, just trying to figure out a way to be safe. I was never panicked and its possible the gauge was a little lower than 1800 at the turn as it was an old gauge, old gear. I was pinned to watching it as we swam in and yes it did get hard to breathe the reg and empty tank started to want to pull me towards the surface. Was having to fin pretty hard to stay down.

This was our second dive of the week as we did an orignally discovery with this son and my older son two days before. My younger son wanted to go again and my older son had an ear issue so he sat out this second dive. On the first discovery dive it was largely the same as this one. The guide in front, my two boys next to each other behind him and me bringing up the rear. The discovery dive instruction pretty much consisted of ( this his how you clear your mask.....now show me. Breathe through this thing, ......now lets go dive). On neither dive did we discuss air plans, turning, etc. Just followed the guide and told him what our air was. I surfaced with about 450 in the first discovery dive.

You need more practice. That's all.

 

[CT-Rich]

I try to be on the surface with about 750 rock bottom. That will give me gas to inflate my BCD, get squared for any surface swim and a little bit of emergency air if something comes up. I usually plan to exit with about 1000 psi.