Preperation for a deep dive...

[MikeFerrara]

Skip the navy tables.

The dive is best done on trimix.

Unless the wreck is a protected area doing an hour bottom time and a couple hourse deco is pretty risky. In addition the amount of gas you'll need to carry is gonna suck.

In a cave it wouldn't be such a big deal because we'd stage the gas and wouldn't have to worry about weather blowing in. In open water we pretty much keep all our gas with us.

Pentrations on scuba aren't like commersial diving. Get some cave and trimix training.

If you keep your bottom time to 30 minutes or less then it's just a nice afternoon on the water.

 

[Seabear70]

Ok, how about this as a kind of a general plan....

Understand, I've been working on this all of one day.

Day one, two teams of divers go down and inspect the ingress and egress points as planed from the plans for the ship. After verifying that the entrances are in fact clear and capable of entry, they tie off downlines at both points leading to marker bouys on the surface.

Day two, the penetration team decends leaving strobes on the downline at the bottom and aprox. 20 ft up. The team then assembles at the bottom and procedes through the wreck.

If on the off chance the planned route was blocked, they would retrace their path to the enterance point using the line they would have tied to the entry point.

Reaching the other side, the penetration team would assemble, they send a liftbag up the downline with a strobe attached to alert the surface support to go to the sight of the second downline, or better yet, the ends of both downlines would already be at the boat, and the lift bag would alert the support team that the penetration team was going into decompression.

Then either using Hooka rigs or stage bottles lowered from the boat along the downline, the support divers would decend to verify that all of the penetration team mad it to the 60' water stop. Failure to reach the stop would send the support team to search for the missing diver, and earn evey member of the penetration team a severe chewing out.

But you are right, trimix would be the way to go. It is likely that this dive could be done on air though. I know I've been at those depths on air before, and for longer than I have planned for this dive.

You did bring up something that I had not thought of though, weather. I'm gonna have to think on that one.

 

[MikeFerrara]

So you're planning a traverse (going in one end and comming out the other)?

You need some cave training before planning this. The bottom time you're talking about is going to require a ton of gas.

There are special prcedures used for traverses to insure that you have enough gas to get through. A traverse requires 2 dives if it will require more than a third of your bottom gas to complete. One to set it up and the other to complete it.

Maybe you've been that deep on air before but it doesn't sound like you've navigated insidea wreck on scuba at that depth. This is a different world. You're commercial diving experience isn't going to do much for you. This isn't anything at all like commercial diving. You'll have a finite amount of gas, no chamber on the boat, no tender and support divers, while handy to have around during decompression (where they can find you), aren't going to worth squate if you have problems inside the wreck.

 

[TX101]

This sort of dive is quite difficult...

Not so much the depth, but the depth combined with a long bottom time (60min) and penetration. v-planner gives me around 2 hours deco using 50% & 100% and 18/45 bottom gas. Your problem will be bottom gas though. You will need at least twin 12's (95's?) and another two as stages (containing backgas), as well as your two stages for deco gas. 6 bottles is alot of gas - and that dosen't leave much for contingency. Also, all those tanks will slow you down in the wreck.

You're adding alot of risk for the long bottom time. Cut bottom time to 40min, then it's a reasonably do-able (although still very dangerous) dive. You cut deco obligation down to 80min and run time down to around 2 hours. You will also be able to drop a bottle of back gas.

Also, the fact that you're asking these questions kinda says that you don't have the training, as planning these sort of dives is part of the course. I don't know your current level of experience on OC, but I know I wouldn't be able to do this dive with a 1 hour bottom time a year from now, or probably even 2 years. Im currently planning dives in the 140' range with a bottom time of 30min (not yet trimix trained).

 

[Caver95]

210ft on air would give you a ppo2 1.55 and you want to do 1 hour, if you dont know why I am bring this up, go and get some trainning. Tec diving is very different from what you used to do.

 

[DA Aquamaster]

But you are right, trimix would be the way to go. It is likely that this dive could be done on air though. I know I've been at those depths on air before, and for longer than I have planned for this dive.

You did bring up something that I had not thought of though, weather. I'm gonna have to think on that one.

Your use of the word "air" scared me in an earlier post and your comments on this one don't make me feel any better. I am probably one of a small and ever shrinking minority of deep air divers on this board and that is only because the max depth of most of my dives is around 150'.

Even at 150' ft I would not even dream of attempting to penetrate an aircraft carrier and to plan to do it at 200 plus ft is, in my professional opinion as a mental health counselor, insane. In fact I have had clients with suicide plans that were not nearly as potentially effective as this one.

The weather concern is very valid. If the weather brews up all the surface support you are counting on is going to evaporate and the longer the run time, the greater the odds of that happening and the greater the consequences if it does happen.

It is a far smarter to take everything you are going to need with you and keep it with you. If you are going to keep it practical, that is going to mean a much shorter bottom time of 20-30 minutes.

Surface supplied O2 for deco is a good idea and you will want to have it available at 20' under the boat. But do not plan on it being there and conduct the dive and configure yourself accordingly so that if it is not there when you arrive, or if you are unable to get back to the ascent line (it will after all be an 880' wreck), you will still be able to meet your deco obligation and ascend safely on the gas you are carrying.

It also sounds like you are sort of planning on a new wreck, no silt and pristine visibility. It is another thing that I would not count on no matter how new the wreck may be. One good storm and silt will find it's way everywhere in the wreck.

This is going to sound harsh, but it is going to be a few years before I can get there and I really do not want to arrive only to find penetration is restricted or forbidden due to a rash of deaths by untrained and ill prepared divers. What you are talking about is a major penetration, one that will need to be worked up to over several months if not years and over numerous dives to achieve an intimate familiarity with the wreck.

 

[DORSETBOY]

I worked briefly out in cyprus, my understanding is that the zenobia (a sunk ferry in relatively shallow water) has seen people die penetrating what many still consider to be a relatively easy dive through the central cargo deck. People have become disorientated and unintentionally got themselves lost in side corridors for example. An out of air emergency at depth is bad enough but it would scare the hell out of me in an overhead environment at depth.

With the depth you intend and diving on air for that duration it sounds like you're setting yourself up for a heck of a lot of deco.

 

[Diver0001]

....snip....
As I see it there are five aspects to a deep dive involving inwater decompression...

1. Mental, emotional comfort in the dive, familiarity with equipment, dedication to the training and dive, etc...

2. Physical, developing the skills and the level of physical fitness nessecary to complete the dive safely.

3. Equipment, chosing and learning to use the proper equipment for the dive.

4. Planning, the dive, supplies, support, etc...

5. The dive itself. This is just a part of the process, and to see it as the end is probably dangerous.

....snip....

On point #4 you've filed almost everything you need on planning under "etc...". It's good to go into this one in detail. It's very different in tek diving than what you might be used to.

Also, you missed "choice of buddy". This can make an enormous difference to your safety (positive and negative).

And finally "procedures" (not the same as planning, the difference is like "what" and "how").

R..

 

[Seabear70]

Ok, maybe I'm not quite ready for this kind of dive.

What do you all recommend for preperation.

As I said, I want to do this, but I want to survive the experience.

I'm pretty familiar with diving wrecks, though almost all of that has been on surface supply. And the scuba experience on wrecks has not been to this depth.

 

[matt_unique]

Ok, maybe I'm not quite ready for this kind of dive.

What do you all recommend for preperation.

As I said, I want to do this, but I want to survive the experience.

I'm pretty familiar with diving wrecks, though almost all of that has been on surface supply. And the scuba experience on wrecks has not been to this depth.

With your experience clearly some things should be very easy for you. Take the training to make sure you cross the t's and dot the i's. You will be that much more prepared when you decide to make these dives. Build your experience up to this monster dive.

--Matt