Key West Dive Ops - Can I do morning reef dives?

[sportxlh]

I've done a little over a dozen dives on the Vandenberg, all on nitrox and I've never gone below 110'. If the current isn't too bad, there are parts of the wreck to see that are as shallow as 70 feet (on the tower where the Duvall Street sign is located). If there is a bunch of current, you'll probably be in the 90'ish foot range near the deck, though parts of the superstructure are much shallower: if you stick to just the superstructure and the radar dishes, you can probably stay in the 80-85 range.

I've done some shallower and conservative profile dives when there was no current and, including the ascent, have done over 40 minute dives with plenty NDL time left on the computer: I dive PO2 of 1.4. Captains Corner does not baby sit divers and they'll let you dive whatever profile you think is appropriate for your skill and gas mix. When I've dove with them, they just told me when the planned to detach from the mooring ball and I had to ensure that I was back on the dive boat by that time after the second dive. I planned my dive times and surface interval times.

I've experience vis of nearly 100 feet and as bad as 30 feet and anything from no current to ripping current.

 

[guyharrisonphoto]

+1 for captain's corner as an operation that does not babysit and allows you do dive your plan, or follow your computer, so long as you are back on board by the designated time.

I know you wanted reefs, but for a morning "quickie" dive off a cruise ship, the Vandy is by far the best dive you will get in KW through a regular dive operator and not a custom charter. I dove it with 32, but kept my depth shallower than 95 (best superstructure is there anyway), and followed my computer (PO2 set for 1.4). No issues with arbitrary dive times or the like.

 

[idocsteve]

"Can I dive the Vandenberg on Nitrox or no?"
Yeahbut.
If you use 32 as Wookie suggests, I think that gives you 111' at 1.4, but only 101 feet at 1.3. Making your safety margin slim.

1.6 is more than enough of a safety margin.

There is not ONE single case of confirmed oxygen toxicity in open circuit scuba diving, even using 1.6 as your baseline.

 

[Rred]

I don't know the statistics, just that DAN suggests 1.4 is generally safer and more appropriate, especially for those of us who are not young USN members engaged in combat operations. And while DAN is not perfect, their knowledge of the issue is generally higher than most other sources.

I'd rather surface early, than sit in a wheelchair saying "I shoulda cut my bottom time." Just a personal choice.

I find the whole area of non-military DCS and the rather casual industry attitude of "proprietary" unverified algorithms to be somewhat less than inspiring confidence. Although, I'm pleased to see that after many years, some dive agencies have finally started to admit that there is indeed a need for "cold water tables" or similar adjustment. Something that for many years, every dive shop and boat operator denied.

So much for who to trust, eh?

 

[idocsteve]

I don't know the statistics, just that DAN suggests 1.4 is generally safer and more appropriate, especially for those of us who are not young USN members engaged in combat operations. And while DAN is not perfect, their knowledge of the issue is generally higher than most other sources.

I'd rather surface early, than sit in a wheelchair saying "I shoulda cut my bottom time." Just a personal choice

If you exceed the O2 toxicity levels and get hit, you won't be in a wheelchair.

 

[DjDiverDan]

If you exceed the O2 toxicity levels and get hit, you won't be in a wheelchair.

No. You'll probably go into convulsions, spit out your regulator and drown. Or, if you are lucky, just black out and drown. Thanks, but no thanks. I'm an old fart who would prefer to keep diving, so I'll use very conservative safety margins. A PO2 of 1.4 is the limit that I'll stick to, and if there's more than minimal exertion involved, having to swim against a current or fight significant surge, I'll aim for a PO2 of 1.2 or less.

 

[idocsteve]

No. You'll probably go into convulsions, spit out your regulator and drown. Or, if you are lucky, just black out and drown. Thanks, but no thanks. I'm an old fart who would prefer to keep diving, so I'll use very conservative safety margins. A PO2 of 1.4 is the limit that I'll stick to, and if there's more than minimal exertion involved, having to swim against a current or fight significant surge, I'll aim for a PO2 of 1.2 or less.

Why do you think that exerting yourself puts you at greater risk for O2 toxicity and that you need to compensate by lowering your exposure limits?

 

[DjDiverDan]

Why do you think that exerting yourself puts you at greater risk for O2 toxicity and that you need to compensate by lowering your exposure limits?

Because that is what all the scientific studies say. There was a very good article in Alert Diver, the DAN publication, regarding oxygen toxicity, and exertion was one of the most important risk factors. See Alert Diver | Understanding Oxygen Toxicity

Central nervous system (CNS) oxygen toxicity is the greatest risk to divers, since it can occur relatively quickly, and the symptoms are siezures, convulsions, and blackouts. While there are other types of oxygen toxicity, including pulmonary toxicity (affecting lung function), those types almost always result from much longer exposures to high PO2, and don't result in symptoms for several hours. With respect to CNS oxygen toxicity, the Alert Diver article had this to say:

"Symptoms of CNS oxygen toxicity, which include seizures, may occur after short exposures to partial pressures of oxygen greater than 1.3 ATA in exercising divers, which equates to breathing pure oxygen at 10 feet of seawater. Resting divers in comfortable conditions tolerate 1.6 ATA of oxygen well."

So, while a PO2 of 1.6 might be fine if I'm just drifting with the current on a Cozumel drift dive in 82 degree water, I could be in real trouble at a PO2 of only 1.3 if I'm working hard to fight a current in 70 degree water (cold is also a risk factor; your body adapts to cold by increasing metabolism to generate heat to maintain core temperature, and this increases vulnerability of nerve cells to high O2 exposure).

 

[Capt Jim Wyatt]

Why do you think that exerting yourself puts you at greater risk for O2 toxicity

Because it is true.

 

[Rred]

Steve, I'm so relieved to hear that.