Best Way to Conduct Deco Stops at 20' When Waves and Currents are Present?

[ldeleon68]

I want to share my story with you so you can give me some recommendations:

This last weekend I conducted a dive to 166' deep that required a 14 minutes deco stop at 20' (last stop) using 99% O2 (Buhlmann GF 30/80). The waves were around 2-3 feet and a strong current was present.

I had planned to grab the line from the wreck to the vessel in the surface. When I reached the 20' mark, I thought I had adjusted my buoyancy when I started switching to the last deco bottle (100% O2)%, then I realized my computer was flashing (red numbers); I was going to the surface!

In the rush of finding the air deflator, I started blowing out all the air in my lungs; but, it was too late, I had my head above the water!

I never entered in panic; but, I thought I might pass out at any moment. I did not feel any symptom in the 1 second it took me to decide to go down again and restart the deco process at 40'.

When I completed the stops and got back in the boat, I tried to understand what happened with other divers. Someone said:"the line lost tension", that I had, probably, more air than necessary in my wing, "that is why I don't grab the lines, etc."

As of today (+48 hours later), I have no signs of bends; what bothers me is, what should be the best way to complete deco stops at 20' when waves and currents are present (deploying the safety sausage to stabilize, swing around all the time? What about doing the last deco stop at 25'-30'? I am not used to do decompression stops in open water but in caves, again, your advises are welcome.

 

[Subcooled]

I have done several (more than one) dives at sea. And thrown up about every time. Let me ask a few questions nevertheless.

How much would 10 minutes at 30ft have cut your required deco at 20ft?
What if you had used nitrox 80% at 30 ft? (it would still have been 1.6 ATA ppO2)

 

[tbone1004]

I don't....
Last stop on 80% to stay out of the surge. Not as good deco efficiency as 100% obviously, but it's not the worst thing in the world.

 

[pickens_46929]

My original deco training call for deco stops up through 10 ft. which would have made this situation particularly rough. I've found that sometimes you have to do slightly deeper stops (22 ft. vs. 20 ft.) or simply plan for deeper stops (no 15 ft or 10 ft.) initially when you know it'll be rough. A Jon line helps save your arms for sure. Proper trim and making sure you're cleaned up gear-wise helps too. Lastly if it's planned for, drifting deco helps avoid all of this - it can be a little unnerving at first but floating under a lift bag is a heck of a lot easier than having my arm yanked out of its socket.

 

[tbone1004]

deco at 10ft from what I understand offers no benefit other than a slower ticking O2 clock, which is important on wicked long dives, but for relatively short dives, there is no advantage, so I try to avoid them if at all possible in the ocean...

 

[tomfcrist]

deco at 10ft from what I understand offers no benefit other than a slower ticking O2 clock, which is important on wicked long dives, but for relatively short dives, there is no advantage, so I try to avoid them if at all possible in the ocean...

Well there is a 20% decrease in gas consumption.....that's pretty huge on long dives as well.

 

[decompression]

This is a common situation I run into, both shore with current dives and boat with current and waves. When I know the probability of waves/current or if it just happens I'll mod the deco plan for deeper stops on 50%. More than likely I'll have sufficient cuft, if not you can either use a Jon line and use the O2 or back gas deeper/longer.


Sent from my iPhone using Tapatalk

 

[ldeleon68]

For sure, I'm not planning to use 100% O2 any more in open water. Yeah, I'll use 80% for the range of 30'-20'.

 

[DevonDiver]

1. If water conditions make a 6m/20ft stop difficult to hold, re-consider diving that day (or seek a more sheltered site).

2. Use a Jon Line.

3. Lower the O2% of your deco gas (50% is a great option for many reasons), if only using 1 gas.

4. Consider 80%, rather than 100%, for the 2nd deco gas, if used.

5. Choose an algorithm that maximizes the efficiency of that gas/ses (i.e. VPM-B for 50%)



.....and a small note: "Dive within the limits of your training and experience".... conduct non-deco (non-consequential) dives to gauge the variable factors of water conditions, topography, temperature etc... before exposing yourself to the risk of missed/omitted decompression.

 

[PfcAJ]

Call me crazy but I don't think the issue here is where the stop is. The issue is squaring away your buoyancy.