When, if ever is it safe for a diver to make multiple trips from the bottom to surface in one dive?

[Nitrox_DiverNY]

I pop my head up to look sometimes. Had to change End Dive Delay to 10 minutes, or computer will log multiple dives.

View attachment 727401

intersting I didn't even think about the computer doing that. I have not dove this profile myself but I do intend to try ill keep the computer in mind

 

[J-Vo]

Several years ago, my wife and I were in Cozumel. One day a couple that had been on the dat boat with us for most of the week decided to book a Lion Fish hunting trip with some locals. That evening we got a knock on our hotel room door, the woman was covered in hives and they were looking for some Benadryl convinced it was an allergic reaction to eating Lion fish for dinner. It didn't really look like that kind of hives to me, and here PDC had logged something like 35 dives in the 30' range. We convinced them to go to the hospital and she ended up riding the chamber the next day rather than the airplane.

These kind of profiles are not what the algorithms are designed for. It's always best to limit the number of assents to the minimum required to safely execute your dive.

 

[SlugLife]

You are right there is a ton of change in the last 15ft, and going slow is probably a very smart move. When you say feeling sick, do you mean nausea? If so this is cause by the pressure change and not nitrogen? Thanks for your feedback t was very helpful!

One or more of: tired, nauseous, headache, light-headed, and/or decreased-responsiveness (like narcd). Similar symptoms to being dehydrated. Tired is probably the most common symptom, which usually hits me after I get back to the boat.

After being much, much, much slower during my 15-0 ascents and avoiding depths greater than 30ft, these "bounce dives" haven't really been much of a problem recently, even if I surface more times than I used to. If I "bounce" many times, I'm usually sticking 20ft or less.

Think of it like being slapped on the arm. A single moderate-slap is annoying, but not a big deal. 20 moderate slaps in a row will probably cause a bruise. However, 20 very light slaps may be equivalent to a single moderate slap.

The goal is to minimize rapid and repeated pressure-changes. If you are increasing frequency, you can somewhat mitigate by reducing the severity. That said, there is still some level of danger (see jvogt's post above) so don't overdo it, so maybe start with 3 times on a couple and see how your body responds. Then slowly ramp up.

You'll also want to "master" bouyancy control and neutral bouyancy since remaining neutral is many times harder near the surface, and the goal is to surface very slowly. I usually start slightly negative, and then fin-up, and orally-inflate only a little bit on the surface, if I intend to go back down almost immediately.

 

[DiveProKoko]

Yes, it is fine to do a dive like that within the no-stop time, by definition of no-stop time. If you are using a computer (correctly), it will keep you safe on dives like this. With a slow ascent rate, I'm aware of no evidence that repeatedly descending to 30 feet, ascending to the surface, and then descending again for an entire tank can cause DCS... it might bother your ears or sinuses though, especially if you're congested.......

This is spot on. To the OP...Keep in mind that assuming you don't linger at the surface, this is ONE dive with varying depths, and your computer will (should) calculate it as such. Ascent rate is the main factor here. SSI deems a dive with less than a 10 minute surface interval a "continuous dive". FWIW - After ten minutes and before 12 hours, it's then a repetitive dive. Happy diving!

 

[tursiops]

your computer will (should) calculate it as such

On some computers (like Shearwater), this needs to be set, otherwise you might end up with multiple "dives" each time you come near the surface (typically 5 ft or 1.5m). I've set ten minutes on my computers.

 

[BlueTrin]

If the Shearwater will continue to decompress the tissues using 1ATM at the surface, it’s mostly cosmetic to have it count as 1 or 2 dives, isn’t it?

 

[DogDiver]

Just some advice here. Instead of asking all these couch and internet divers and getting multiple conflicting answers. Call DAN and ask them. They will be more than happy to answer your questions with accurate information.

 

[Nitrox_DiverNY]

Several years ago, my wife and I were in Cozumel. One day a couple that had been on the dat boat with us for most of the week decided to book a Lion Fish hunting trip with some locals. That evening we got a knock on our hotel room door, the woman was covered in hives and they were looking for some Benadryl convinced it was an allergic reaction to eating Lion fish for dinner. It didn't really look like that kind of hives to me, and here PDC had logged something like 35 dives in the 30' range. We convinced them to go to the hospital and she ended up riding the chamber the next day rather than the airplane.

These kind of profiles are not what the algorithms are designed for. It's always best to limit the number of assents to the minimum required to safely execute your dive.

wow, so in reality she was up and down off the bottom 35 times in one dive. I can see maybe doing it once or twice in special situations if truly needed, but 35 time is nuts. I guess she was dropping the fish back to the boat every time she got one? thanks for sharing

 

[Nitrox_DiverNY]

One or more of: tired, nauseous, headache, light-headed, and/or decreased-responsiveness (like narcd). Similar symptoms to being dehydrated. Tired is probably the most common symptom, which usually hits me after I get back to the boat.

After being much, much, much slower during my 15-0 ascents and avoiding depths greater than 30ft, these "bounce dives" haven't really been much of a problem recently, even if I surface more times than I used to. If I "bounce" many times, I'm usually sticking 20ft or less.

Think of it like being slapped on the arm. A single moderate-slap is annoying, but not a big deal. 20 moderate slaps in a row will probably cause a bruise. However, 20 very light slaps may be equivalent to a single moderate slap.

The goal is to minimize rapid and repeated pressure-changes. If you are increasing frequency, you can somewhat mitigate by reducing the severity. That said, there is still some level of danger (see jvogt's post above) so don't overdo it, so maybe start with 3 times on a couple and see how your body responds. Then slowly ramp up.

You'll also want to "master" bouyancy control and neutral bouyancy since remaining neutral is many times harder near the surface, and the goal is to surface very slowly. I usually start slightly negative, and then fin-up, and orally-inflate only a little bit on the surface, if I intend to go back down almost immediately.

good to know, the slap analogy was right on. great stuff you provided!! thanks

 

[Nitrox_DiverNY]

Just some advice here. Instead of asking all these couch and internet divers and getting multiple conflicting answers. Call DAN and ask them. They will be more than happy to answer your questions with accurate information.

never thought about asking DAN something like this, but ill keep that in mind. Most folk here seem quite consistent and have always been helpful. Thanks