To deco or not to deco

[Tom_Ivan]

There is a popular thread (bad buddies) going at the moment and I wanted to take the OP's post off on a tangent.

To summarize, the OP and his buddy were diving in rough water with a fairly strong current. They were also riding their deco limit quite closely. Near the end of the dive the OP, to avoid going into deco, surfaced from where he was without first locating the anchor line. This meant that he surfaced some distance from the boat and had a 30min surface swim to get back (in rough weather). The OPs buddy on the other hand went into deco (we assume), located the anchor line and was able to surface straight onto the boat.

So... What would you do (assuming you have sufficient air)? Do you think a rec diver in a similar situation should avoid deco at all costs? Even if it means ending up far from the boat/out of sight of the surface crew or (if your confident that you know where you are), remain on the bottom, find your reference (anchor line, wharf, cliff face etc) and surface exactly where you want to?

 

[Kevrumbo]

On a recreational single tank dive within NDL, I only plan to have enough gas reserved for an emergency gas share contingency to bring myself and a buddy up from operational depth through to the requisite safety stop(s) and finally the surface. Once I encroach on this Minimum Gas Reserve SPG Value, my buddy and I start our nominal ascent to shallower depths, and hopefully together we are still able to directionally search for & locate the anchor line.

If we still can't find it and gas pressure remaining is approaching 50 bar, I'll launch my DSMB from as deep as 9 to 12m, so the boat crew can see & track us early as we ascend to and complete our 6m safety stop. If we have a long surface swim, so be it --ideally the boat crew having spotted the DSMB early can now pull anchor after recovering other divers, motor over and come meet us halfway. . .

 

[Oldbear]

No Dive Limits are all theoretical and based on "average" diving. If a dive became strenuous for what ever reason, then theoretically the diver will reach or exceed the NDL sooner than planned or what a computer might be telling you. It sound like from the OP's description of the dive those divers potentially could have exceeded the theoretical NDL.

Kevrumbo makes good points in putting an additional safety factor into his dive plans ... a contingency for when things do go upside down.

 

[Rechno]

I would say it depends on the circumstances. If i know where I am and that the anchor line is nearby and know that there is a strong current to encounter while ascending, I would go for a little deco in order to reach the line and not do a drifting ascent.
However, if I feel lost and dont know exactly where the anchor is... or if it would take me in a longer deco, I would shoot the SMB and drift. Wasting time on searching the anchor might otherwise get you into trouble.

 

[rhwestfall]

It seems that this was a poor/non-existent dive plan.... or wasn't modified to adjust to factors encountered.

OW 101 - into current for first leg, returning with it, theoretically using less gas on the return leg.

That being said, recreational diving is NDL diving, and if this was to include NDL violation, plans needed to be in place, including proper gas quantities for the dive. If there was no full knowledge of being able to complete the dive within the parameters present, it is "shoot a marker".

 

[jfe]

A 30 min swim back to the boat is a long way off. Rough weather is a loose term, what exactly is rough weather, choppy seas, high swells, strong surface current? IMO SMB and surface, keep eyes on boat and try and signal if you have the means to, going into deco while searching if your already "lost" does not serve any purpose, I would say only if you are 100% certain and can get right back to the anchor line and have the gas, do it, but if your unceartain rather surface.

 

[RainPilot]

If you leave the bottom on a recreational dive and don't do a crazy slow ascent, you shouldn't rack up any additional deco. Once you get to 15-20 feet, you should have quite a bit of NDL left since you are pretty much only off gassing.

I would suggest that ascending towards the line, followed by a level swim at safety stop depth toward the line (gas permitting) should allow for the best result. Once gas hits critical, surface.

 

[100days-a-year]

More people die/get lost coming up far behind the boat than suffer any consequence doing what would be minor deco.Should not even be a consideration to bolt and hope you get found when there is an anchor rope nearby.

Also pick better buddies or proceed to the upline on your own at your turnpoint if they go cowboy on you.

This assumes the initial premise of adequate air reserves.

 

[Bob DBF]

This meant that he surfaced some distance from the boat and had a 30min surface swim to get back (in rough weather)

A long surface swim is involved in a lot of my dives so I'm not afraid. Also the surface is safer than doing deco if you don't have the knowledge, training and gear to insure a positive outcome. Having a deco obligation without the gas to do it may turn out ok, or it could be a chamber ride, or worse.

I've done quite a number of swimming safety stops described by @RainPilot, and they work well.

Deco is a good choice if you had the gas to do it, and I would want to be carrying enough redundant gas to pull it off, but I'm getting conservative in my old age.



Bob

 

[TMHeimer]

I won't give advice on the deco other than that the surface swim seems better. I don't boat dive much at all, but have to wonder how you got a 30 min. swim away. A factor may be your location--Are you in a place with some boat traffic, or out in the boonies like where I am? ie. You could miscalculate with compass use if you can't actually see the boat. A compass swim underwater for that distance could easily get you turned around as well.