Shallow beach diving

edasque

Hi guys,

going to dive at a local beach on Sunday. Depth expected to be 15 to 40 feet. Never dove my Rebreather at such shallow depth before (except the pool obviously).

What would you suggest I keep my PPO2 at ? I was thinking about setting the solenoid to .7 and maintaining a PPO2 around 1.0 ?

Thoughts ?

Erik

Yevgeniy

I do this kind of diving for 60-90 min. quite often and always use automatic setpoint at 0.7.

JCdesign97

Hi Erik,

Curious to hear how you made out on the beach dive with your Optima. I've done my fair share of beach diving off of the NJ coast (on OC), so I have an idea what kind of conditions you likely encountered. I saw your post yesterday and I didn't want to rain on your parade, but just from my experience I had pretty much decided that I won't ever do a beach dive on CCR.

My initial reason was mainly because of the amount of sand churned up in the surf zone - you just can't imagine how much sand gets in everything and where it gets. Regs practically need a rebuild, inflators are sticky, valves are crunchy when you turn them, etc. I had made up my mind that the Optima has too many intricate pieces to subject to that kind of abuse. Also you are likely to get planted and rolled when you exit, unless conditions are perfect ... so the sand just gets that much worse.

Now that I have a bit of experience diving the Optima, though, (still a newbie, mind you) I can also say that using it as shallow as a beach dive seems like it would be a pain unless you kept the setpoint low - like 0.4 or 0.7. Anything more and the solenoid constantly injecting to maintain setpoint and the corresponding bouyancy fluctuation seem like they would be more trouble than it's worth, but maybe I'm wrong.

Hope you had a good dive and curious to hear how it went.

Cheers,

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Cheers,

John

curator

Hi All,
I've dived an inspo with a hammerhead on several very shallow shore dives (10-15 feet). Set my setpoint at 0.7 Made myself little overweighted and had a great time.

(Luckily, aroud Dorset its more shingle than Sand - not too many problems with getting rocks in your regs )

The Hammerhead kept the setpoint perfectly.

Cheers

Curator

edasque

So I dove to 18 feet for a (very) short while and was underweighted. With the optima, dry suit, LP27 and 6 pounds on top of the Rebreather, I was too buoyant.

O2 injection induced buoyancy changes seemed manageable (I was at .7, I felt I could breathe down .4 too quickly at 18 feet, 1.3 ATM) but I really can't tell as I was grabbing rocks to stay down.

I'll either put 12 pounds total in the Rebreather pockets (I think that's the max) or get a weight belt / transpac weights.

More later, I guess.

zoo_diver

If you are working in a shallow depth like this -- can't you put your SP way low (.4) and manually fly it at .7 or more? If you have a lower SP, you can avoid the auto O2 injection and shifts in buoyancy.

edasque

Well, the shift in buoyancy hasn't been a problem, it was my weighting that was. I was way under weighted even with my CL at minimum volume (inhaling).

I have to figure out the best weight and weight distribution for those conditions first. I hope to get 0.7 working at this point as I don't want to be around .4 at those depth (not descending), that's too close to normoxic for my comfort.

I feel that .4 at the surface is ok for a short period of time, knowing that you're going to get to 30m quickly (4 ATM) and your PPO2 is going to be high at that point before you switch to your bottom PPO2 but wouldn't you breathe out .4 at 3 meters very quickly towards normoxic (which could really mean hypoxic if you take into account potential O2 sensor linearity problems ?)

babar

Just turn off the dil altogether, and dive it as an O2 rebreather. That's what I do on shallow beach dives. Easy to do, no big bouyancy shifts, and almost no way to become hypoxic

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Babar
Evolution Plus
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Tom Rose

I shallow dive rebreathers all the time. Set point...I use MCCR....if the depth is 30 feet or less I dive on pure O2 but do not completely clear the CL of air. I use a PPO meter and make sure I do not ever go over 1.4. If the PPO at 30 feet is 1.4, it is going to be about .7 at the surface. Think about it....

Using the orifice systems that Duncan, Sutton, and I use, there is no problem diving this way.

It still beats the hell out of OC as two hours of diving gear weighs under 20 pounds.

Tom

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edasque

So I finally did a successful beach dive (had some equipment problems before). Ran the o2ptima at .7 and manually flew it to around 1.0. Maximum depth was around 13m (42 feet), dive duration was 70 mn.

Saw a bunch lobsters, a massive sea raven, a skate flying by and a YBOD. Also saw a toad crab for the first time. I really love seeing a sea creature I have never met before, makes my dive.

The O2ptima behaved really well and didn't seem sandy at all when I disassembled it. I dove with an AL40, sidemounted to my Nomad, which though unnecessary was a good practice for deeper dives.

Dove the O2ptima with 5 pounds in each pockets which seemed fine. Used 300 PSI of O2 (LP27). Was at Folly Cove, in Gloucester MA, left side.