Mild down current.
2 Russian tourists died while scuba diving in Verde Island in Batangas City
- Thread starter chaad
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Dan
Contributor
At 2.2 it certainly will but in this scenario there's a good chance you'd be OOG before that happens.
U.S. Navy Diving Manual, Revision 7A, 30 April 2018.
Figure 17-4...
Oxygen Toxicity Limits & Symptoms
Oxygen toxicity limits can be very confusing, especially for PPO2 (Partial Pressure of Oxygen) levels above 1.6 ATA used in chamber-based hyperbaric treatment (recompression) and decompression tables. For example, here is a chart of one of the most common DCS (Decompression Sickness) treatment tables. Note that the PPO2 of pure oxygen at 60'/18.3M is 2.82 ATA — or more than twice the normal limits recreational divers observe.U.S. Navy Diving Manual, Revision 7A, 30 April 2018.
Figure 17-4...
Deleted, wrong area.
Steelyeyes
Contributor
Wow. My wife and I were diving that area two weeks prior to the incident. Our dive guides were pretty wary of situations like that and were very serious about none of us getting in front of them.
Condolences to the families of the divers involved in this accident.
The only speculative comment I can add that I haven't seen in the thread so far relates to the diver found on the surface with a fully inflated BCD and an empty tank. Given the descriptions that others have given about how terrifying the down current situation could have been, this might be the case of the diver having hit the inflator while at depth, and never let go. I can easily picture a AOW diver (no offense to AOW divers intended....I'm using that as shorthand for someone who probably doesn't have 1000s of dives) trying to inflate to counteract the down current, and if it doesn't immediately seem to work, they just fixate and keep cranking. The overinflation valve would quickly kick in and you'd possibly just "burp" your supply in very little time at depths like that......and you'd eventually end up on the surface with a full BCD and 0 gas.
For those who have been asking about suggestions for handling down currents...the ones that happen here sound worse than I have experienced, but here's some points to contribute to this part of the convo.
All of the down currents I've experienced have been on walls, during tide exchanges (which makes sense, right?). There are a few spots around Palau where this is common. If it's a big tide/big moon, extra caution should be taken. I've seen crazy things happen around Peleliu on New or Full moons. There at least, I have generally noticed "something coming" before getting into the down current. You're drifting along the wall, when up ahead you either see all the fish suddenly turn toward the surface and (try to) haul ass. You might also see soft corals or sponges on the wall waving differently than they are in your current position. Or, you might see a flow of sand from topside on the reef spilling down. You don't normally see that on these dives. In other words, be on the lookout for anything unusual. Note that "upwellings" are also just as common....so all the same tips, in reverse.
In Palau, these currents TEND to be pretty narrow "channels," so if you can hang on to something (not reef-friendly for sure, but safety first) and go "hand-over-hand" for a bit, you can get to the margin where it's possible to make progress across the current. Having said that, I've been in one upwelling there that seemed to span the entire corner and we were all "blown" up the wall and onto the reef flats. Luckily nobody was hurt beyond some scrapes, some "straightened out" reef hooks and everyone's wetsuits needing a good rinse. That was the highest tide exchange day of the year.....and a lesson learned.
The only speculative comment I can add that I haven't seen in the thread so far relates to the diver found on the surface with a fully inflated BCD and an empty tank. Given the descriptions that others have given about how terrifying the down current situation could have been, this might be the case of the diver having hit the inflator while at depth, and never let go. I can easily picture a AOW diver (no offense to AOW divers intended....I'm using that as shorthand for someone who probably doesn't have 1000s of dives) trying to inflate to counteract the down current, and if it doesn't immediately seem to work, they just fixate and keep cranking. The overinflation valve would quickly kick in and you'd possibly just "burp" your supply in very little time at depths like that......and you'd eventually end up on the surface with a full BCD and 0 gas.
For those who have been asking about suggestions for handling down currents...the ones that happen here sound worse than I have experienced, but here's some points to contribute to this part of the convo.
All of the down currents I've experienced have been on walls, during tide exchanges (which makes sense, right?). There are a few spots around Palau where this is common. If it's a big tide/big moon, extra caution should be taken. I've seen crazy things happen around Peleliu on New or Full moons. There at least, I have generally noticed "something coming" before getting into the down current. You're drifting along the wall, when up ahead you either see all the fish suddenly turn toward the surface and (try to) haul ass. You might also see soft corals or sponges on the wall waving differently than they are in your current position. Or, you might see a flow of sand from topside on the reef spilling down. You don't normally see that on these dives. In other words, be on the lookout for anything unusual. Note that "upwellings" are also just as common....so all the same tips, in reverse.
In Palau, these currents TEND to be pretty narrow "channels," so if you can hang on to something (not reef-friendly for sure, but safety first) and go "hand-over-hand" for a bit, you can get to the margin where it's possible to make progress across the current. Having said that, I've been in one upwelling there that seemed to span the entire corner and we were all "blown" up the wall and onto the reef flats. Luckily nobody was hurt beyond some scrapes, some "straightened out" reef hooks and everyone's wetsuits needing a good rinse. That was the highest tide exchange day of the year.....and a lesson learned.
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