How Deep?

[greg somers]

Hey Hocky,
My deepest was 120' and it wasn't planned. I was at the Poor Knights and the vis was over 150'. That brings it's own issues. I was keeping a certain level above the bottom but forgot to account for the bottom gradient dropping away gradually. An 80' dive plan turned into a 120' one. Luckily I had read my tables and knew the bottom times for deeper depths. Something I'd recommend as computers can fail on you. Deep diving is great for wrecks and certain features of interest but as others have mentioned you need to build up your dives. I'm a bit of a rare cookie. My ears equalise by themselves and I haven't been narced yet but that doesn't mean that I don't plan for it. A good rule of thumb is to dive in daily increments. 25m day 1, 30m day 2, 35m day 3 etc.. and do 2 dives per day with experienced divers. In my experience there are more divers at depth by accident than by planning. Other consideration are water temperatures at depth and how they differ worldwide. The cold factor needs to be thought out. The location for the dive is important aswell. Diving down features, walls, anchor lines help immensely. 'Down with the Wallabies' and 'Up with the All Blacks' and Pharlap was from N.Z. From the gasman.

 

[Sundiver]

I hope you're just asking for research purposes. Lots of people have done it and not come back. Lots. So, for informational purposes only...
As a commercial diver (surface supplied, hardhat) I've worked quite a bit as deep as 240fsw for 30-40 minutes. Narcosis is definitly a problem. As a thrill seeker I've done lots of single tank (with a small pony) pops to 300-320fsw on air. I would never risk a buddy for something like that. I don't tell anyone before or after. Too much machismo in sport diving. I used to dive with Bret Gilliam some in the late 80's and picked up some bad (but private) habits. I agree emphatically with Mario's post above. The partial pressure of O2 at 320fsw is something like 2.2ata. Convulsions and death can result at those pp's. So far I've come back. Next time I might not. Don't do it.

 

[100days-a-year]

218 on air with doubles after building up to it with dives to 160 and 180 .32% and 80% deco gasses.2 buddies 1 an instructor for tri-mix.This is routinely done to show the advantages and safety(relative)of Helium as a breathing gas as compared to air.I was so narced the 1st minute or so I could barely see.You do however become acclimatized to it.All dives below 130-150 fsw should be done only by those trained for it.People die from exceeding the limits of thier training before they reach the limits of thier common sense.

 

[Mario S Caner]

Hello there Tony, don't think we've met yet. Welcome to the family here at scubasource. Are you doing your trimix diving out in FL?

 

[Hocky]

Hi Guys

Just a note of thanks for those who have contributed to my question "How Deep"?. Your replies have been interesting and insightful. There really is a wealth of knowledge out there and we can all benefit from what others have to say, and more importantly have done.

Please keep the questions and answers coming. I for one am still learning.

Kind regards

Hocky

 

[uwsince79]

Here is a copy of a dive from my log in which we dove to 208fsw on a wreck called the Lowrance it was my deepest on AIR . It is a beautiful wreck and one of the largest artificial reefs wrecks off Florida coast It lays e/w. Avg dive was spent around 165 FSW with one trip to the sand (under 5 min). Viz was outstanding 100' plus, deck has a lot of mono on it.
(This table is not for anyone’s use other than that of Research by Hockey, Deep diving takes a lot of training and experience and should not be done with out it period.) This dive is on AIR 21/79 with a deco switch to 80/20 @ 20 FSW.


For you records:
Depth 208 for 25 min ppO2 1.48 gas used 177 cf
DECO Table
AIR 60FSW for 4 min ppo2 .59 total time (TT)34
AIR 50 FSW for 5 min ppo2 .53 (TT)39
AIR 40 fsw for 8 min ppo2 .46 (TT)47
AIR 30 fsw for 6 min ppo2 1.53 (TT)53
GAS SWITCH
80O2/20N2
20 FSW for 10 min ppO2 1.28 (tt) 63
10 FSW for 16 min ppO2 1.04 (tt) 79
OTU's 140
Ascent time 5 min
Total Deco 49
VS air deco time of 113
Total Gas used 268 cf
exceeded 1.5 ppO2, at rest non working
Hocky hope this helps your research

WARNING
"Mors sola fatetur quantula sint hominum corpuscula"
("death alone discloses how insignificant are the puny bodies of men")

 

[greg somers]

Question,
What was your other gas? 21/70,thats .91 partial?were you using semi-enclosed or full rebreathers or were you carrying alot of tanks? What's the heads up there my friend? Gasman

 

[ericfine50]

Looks like he was diving Air (21% O2) and then 80% O2 for his decompression gas. I would guess he was using a set of double AL 80s? (just guessing because it is Fl. and a ton of rental tanks) and then Al80s for Al40s for decomrpresion gas.

Eric

 

[uwsince79]

Gasman,
It was AIR 21/79, just a typo thanks for the catch.I fixed it already. I was on scuba, no rebreathers. If you look at the gas burn, i did not need more than the dbls and one pony. I hit 208 but most of the dive was around 165 fsw. Sorry for the typo, but I did remark in the opening i was on AIR.
Eric,
As for the tanks they were not rentals (I am a local) I dive twin hp100's (have 2 sets) with 40 cu lp OMS steel ponys for deco (have 4 of these). Hope this helps. I also on longer dives use AL 80's as well for travel and deco.
Hope this helps.

"Difficile est tenere, quae accepteris, nisi exerceas."
(" It is difficult to retain the knowledge you have acquired unless you put it into practice.")
PLINY LETTERS
bk viii, epis 14,c 108 A.D.

 

[ericfine50]

Bobby,

Sorry about that. I was just guessing. For the deco tanks, why not Al 40s? they are lighter and smaller?

Thanks
Eric