dive to 300 ft

[Crush]

Good day,

In the thread Accidents and Incidents > Cozumel Incident 9/4/11 it has been contended that some divers planned to dive to 300 ft on a single AL 80 or AL 100. Regardless of what happened in Cozumel and irrespective of whether or not these rumours are correct, I am curious how properly trained DIR divers would execute a dive to 300 ft. Let's say for a max bottom time of 10 minutes - just go to 300 ft, hang out there for 10 min, then head back. I am not interested in a recipe and I won't be trying this on my own. I'd be curious in a sketch based upon healthy divers with decent SAC rates. For example, would you likely have doubles plus stage bottles? Eight bottles per diver? Trimix? Deco obligations totaling eight hours? Support divers?

Again, please don't waste too much time. I just want to see how very different a DIR approach would be from a "bounce dive."

Thanks.

 

[ScubaSteve]

You can't compare plans for a bounce to 300' and a dive to 300' with 10 minutes at depth. These are extremely different circumstances.


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[boulderjohn]

A quick summary would be that a well planned dive to 300 feet on open circuit would involve an appropriate blend of trimix for the bottom gas and other blends for travel (it would not be safe to breathe the 300 foot gas at or near the surface) and decompression. There would be careful planning for the amount of gas needed to make sure that there was enough gas to ascend safely in an emergency that included a catastrophic loss of gas by your buddy. Everyone would be on the same page in terms of the plan from the start. Everyone on the team would have been thoroughly trained so that they know how to react to specific emergencies, such as a non-functioning decompression bottle. There would be safety systems in place, such as ways to communicate with the surface in case of emergency.

In short, look at everything that happened in Cozumel and ask yourself this question: what would be the opposite?

 

[Cave Diver]

Not a DIR response, but just for your reference I did a similar dive using a rebreather. Trimix diluent, multiple 80's including a deep bailout. Total runtime was right around 3 hours.

 

[Jim Lapenta]

I posted the v planner profile for a ten minute 300 ft dive. That was on air. Not having gone that deep yet due to not having full trimix training I can't give specifics. But as has already been noted a proper dive to that depth would likley involve at least two travel gasses- say a mix good to 130, then a switch to one good to 210 or so, a bottom mix, and the appropriate deco which could be 2 or 3 mixes.

In addition a proper dive to that depth would also involve the use of safety divers to bring deco mixes if necessary, carry used travel gas bottles, and perhaps even provide snacks and drinks to the divers doing the deco.

 

[Crush]

Thanks to everyone except ScubaSteve for the helpful responses on a dive to 300 ft. Thanks to ScubaSteve for the helpful response on why the OP is stupid.

I was trying to imagine the difference in scale (ito the numbers of bottles of gas and deco obligations) between a bounce dive and a proper deep dive. For example, is a "bounce" on an AL100 to 300 ft a 10 minute dive while a proper dive involves gas equivalent to four AL80s and three hours in deco? I am sure that my comparison is imperfect, ScubaSteve . I only ask because I an curious and I am bored.

 

[Jax]

For those that have done > 200' deep dives, aren't most of those done with a support team? That not only do you have all these stages of travel and deco gas, but a support diver who comes part way to check for problems?

Just something I've gathered from reading . . . .

 

[LiteHedded]

For those that have done > 200' deep dives, aren't most of those done with a support team? That not only do you have all these stages of travel and deco gas, but a support diver who comes part way to check for problems?

Just something I've gathered from reading . . . .

I've never had a support diver on those types of dives

 

[PfcAJ]

For those that have done > 200' deep dives, aren't most of those done with a support team? That not only do you have all these stages of travel and deco gas, but a support diver who comes part way to check for problems?

Just something I've gathered from reading . . . .

No. In my experience, its got to be a pretty big dive to require support divers.

 

[Cave Diver]

I've never had a support diver on those types of dives

Or dedicated travel gas.