What Should I have done?

[MidOH]

Blowing your safety stop, or being upside down in it, is kinda embarrassing too.

I'm always slightly negative, to go up. So yeah, dump to climb, and use your fins.

 

[Rilelen]

Not to dogpile, but yes absolutely you should have proactively let both the DM and your dive buddy know your air situation. You are not solo diving. You have a commitment both to yourself and to your buddies. What if your son had had an emergency and needed air? A CESA is exactly that: a controlled EMERGENCY swimming ascent.

It should never be a part of the dive plan. And if it gets to the point where you are considering one, that is something you need to communicate clearly to your buddies (and the DM) asap.

 

[inquis]

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

In the future, make sure you understand the gas plan before the dive. A turn of 1800 psi isn't terribly unusual for an out & back shore dive: if one desires to end with a reserve of 700 psi (but surfacing would be OK, as it sounds like it was in this case), one approach is to use half of the non-reserve gas going out and half on the way in. Assuming perhaps a 2900 psi start, the non-reserve amount is 2200 psi (=2900-700), so use 1100 going out. 1100 off of 2900 is 1800 at the turn. This assumes that any minor usage variations can come out of the reserve.

What seems odd is that you blew through the return gas AND the entire reserve on the way back. It's possible anxiety increased your consumption, your depth was deeper on the return, or you swam faster (or some combination).

Next time, you should definitely signal when you are getting close to the reserve and again at the reserve. If it's obvious you're not close to finishing, signal you want to shallow up to reduce consumption.

Lastly, you need to be close enough to make a couple hard kicks and grab a fin. If the DM is swimming too fast, signal them to slow down. Ideally, you would have been next to your son, both within easy reach of the DM.

I think it's great that you're proactively looking for ideas about how to improve for next time. Good luck, and it's also really cool your son is taking to the sport.

 

[boulderjohn]

What seems odd is that you blew through the return gas AND the entire reserve on the way back. It's possible anxiety increased your consumption, your depth was deeper on the return, or you swam faster (or some combination).

Yes. The turn pressure was very reasonable, and since you were getting continually shallower on the return, you should have used less air coming back than going out.

Some people call this the rule of halves, used on a dive plan that goes one direction, turns, and returns. Your return should use less gas than the first half of the dive because your return is at a shallower depth. You can also monitor you gas and ascend to an even shallower depth at any time you feel the need.

Assuming you started with 3,000 PSI, I would have guessed you would have reached the end point of your dive with maybe 700-900 PSI.

 

[DivingLane]

I think when the DM checked your air after the turn, and saw you were at 1800, they knew you would be fine to make it back in the shallower water and safely ascend. I know our guide in Cozumel thought the same. We told him our air at one point, and to me it seemed lowish, but he had a very good sense of our consumption by then, and knew we were on our way up. He was right, we surfaced with over 500

 

[Mattjcurry]

I probably would have given the low on air hand signal at about 800. Or I would have signaled for a safety stop.

 

[SwimAway]

Throwing in my thoughts here.

Buddy Failure - This feels like a classic "odd man out" scenario. My instructors always say that 3 people is the most difficult number to dive with. It is just hard to stay together. Your son and the DM were "20 yards" ahead of you! They aren't your buddies anymore! You are solo diving. All of the training will say "it is your responsibility to stay with your buddy, not visa versa", but that only works if you both agree on that. Clearly you couldn't rocket forward 20 yard, especially as you were clearly burning through your air already.
So basically you had no buddy anymore, and you had a decision to make.

My inclination in hind-sight here is that I'd "turn the dive" when I was at a point where I knew I'd surface with the reserve I had set before. If none had been set, I'd use 500psi, as that is what the training materials I have say to use as a normal reserve. So when I knew I'd need to surface, with a safety stop, "now" to end up with 500psi at the surface, I'd signal and do so.

As I said before though, with 20 yards distance, you are essentially solo diving, so I'd "just do it".
I'm not sure how to even signal to people 20 yards away. Possibly a good bang on my tank would alert them?

Then the DM should realize he's in a "missing buddy" situation and either come to you if he can see you, or do the "search for 1 minute then surface" routine. There he would hopefully see you were topside.

In a perfect scenario, he'd see you during your safety stop and could join you there and finish the safety stop together, assuming your air lasted.

What I see here is a collision of the "turn the dive any time you want" and "stay with your buddy". If your buddy isn't close enough to turn the dive, they turned you into a solo-diver, and you have to leave them to it. Hopefully they wake up and come to you as they should. If you couldn't see your buddy, the call would be the same, search for at most 1 minute and then surface, and assume your buddy would have done the same having lost sight of you.

---

Regarding, "in 10 feet of water": I'm assuming you didn't pump up your BCD "10 feet down" but that you surfaced "in 10 feet of water". "in X feet of water" means you are in a column of water that deep to me, but I've spent more time on top of sailboats than under them now, so maybe that's just wrong terminology.

 

[rx7diver]

... 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? ...

You want to keep enough gas in your cylinder to be able to safely surface you and your buddy from depth, while both of you are breathing from only your cylinder, at any point in the dive.

And you want to keep enough pressure in your cylinder to keep water from entering it.

An analog SPG might not be accurate at very low cylinder pressures.

Some regulators do not work well--if at all!--if the cylinder pressure gets too low.

If it were safe to do so, being so shallow and so close to shore, I would have gone to the surface with my buddy, after signaling "LOA" to the dive master (and getting his/her "okay"), and snorkeled back in with my buddy and inflated SMB.

I would have left enough gas in my cylinder so that I and my buddy would be able to quickly dive back down NOW if necessary (e.g., to avoid being run over by a speeding boat or jet ski or strafed by a Zero or Messerschmitt).

rx7diver

 

[covediver]

1. Mechanical gages are not always that accurate at low pressure. In my experience they always indicate you have more air than is actually in the tank.
2. Everywhere I dive with a guide (Roatan, Hawaii, etc) the guide wants to know when you are at half a tank, 1000 psi, and the low on air point (usually 700 psi) which allows you to do a three minute stop and surface with 500 psi.
3. I am usually the first to hit the low on air point of the group, so I sympathize with your circumstances. I never try to push a dive, at 700 psi I am looking to head up.
4. I do not recommend doing emergency swimming ascents as part of normal dive planning. I have done one in my life and hope never to do another,
5. Plan your dive, dive your plan. Deviations lead to complications

 

[clownfishsydney]

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.

You should have noticed that you were nearing zero psi as once below the pressure setting of the first stage (normally 160 or so), it would have got harder to breath.