Diving during surface intervals?

[Pearldiver07]

And when you surface from the first dive you're going to have oversaturated tissues and you're going to have a bubble shower in your blood. Normally this is contained by the filter in your lungs. But if you do a bounce dive while you've got this free-phase bubble shower going on, you can compress bubbles enough to get them past the lungs filter and then re-expand them on ascent.

If you're going to do this, the second dive should be terminated by a period of real decompression... so spend much more time coming up (maybe 3ft/min) from the 25 foot dive... to use a similar analogy you need to slowly open the pop bottle, letting the pressure off gradually over a longer period of time in order to open it safely after it has been stirred up...

So, it can be done, but its not a good idea. And I have run into reports on this board of exactly this kind of behavior that has led to getting bent...

Also, don't free dive after scuba diving...

Important point to this argument - that EVERY ascent induces risk, due to the recompression and then repeated expansion of subclinical bubbles in the system.

I don't like the term "surface interval dive" either. It is simply another dive added to you profile. You're reducing the off-gasing in all tissue types, adding another (at least one) ascent and in some tissue types you'd be adding levels of saturation as well.

I fear that unless I've totally misread the intent of the question, is that this is not significant in the day's plan. I hope I'm wrong. Every exposure to compressed gas breathing must be taken seriously, especially when diving deeper for duration.

My 2 bar...

 

[DandyDon]

I don't like the term "surface interval dive..." :silly: It's is a complete misnomer isn't it? It would simply be a dive of marginal safety.

 

[lamont]

I don't like the term "surface interval dive" either. It is simply another dive added to you profile.

Actually, I don't even like the "simply another dive added to your profile" description of this.

You can do the math and determine that based on nitrogen loading a quick 5 minute dive to 20 feet to pickup something you dropped is fine -- no decompression required -- but doing that right after a dive with significant gas loading is asking for trouble, no matter what the residual nitrogen tables say (residual nitrogen is all about dissolved phase gas, not free phase, and the tables don't know anything about lung physiology and filtering, etc).

IMO, for repetitive diving, a 1 hour surface interval should really be the minimum and safety stops should be more like 2 min @ 30,2 min @ 20,2 min @ 10, or at least 6 mins to the surface, even from 20 fsw.

 

[Garrobo]

I like to jump in the water and float around during the SI sometimes, like if I'm on a fastboat without a head or the conversation gets a little boring. Since I'm on the surface I don't figure that that would have any effect. Right?

 

[DandyDon]

Sounds generally ok, Garr: you're not changing pressures, over exerting, or overheating.

But with you listing over 4,000 dives, you should know that...

 

[Garrobo]

!!!!4000 DIVES???!!! I've got just over 100 dives in a year and a half. Where'd you get 4000?

 

[Garrobo]

OK. I see it now. If I say that "I'm a fish" that that means that I've got over 3000+ dives. I guess I'll have to change it to "I'm a tadpole". Sorry to anyone who thought that I was misrepresenting myself. I'll change it now.

 

[visibilityunlimited]

I didn't see anything addressed with regard to free diving during surface interval which (correct me if I am wrong) should not be engaged in as something to do during a surface interval. Snorkeling is ok because you are staying at the surface the entire ime but skin diving (free diving) which is going to depth is a no-no.

 

[lamont]

I mentioned that:

Also, don't free dive after scuba diving...

 

[DandyDon]

OK. I see it now. If I say that "I'm a fish" that that means that I've got over 3000+ dives. I guess I'll have to change it to "I'm a tadpole". Sorry to anyone who thought that I was misrepresenting myself. I'll change it now.

The pull-down menu include increments, as you know, and after >3,000 there is "I'm a fish." It's been requested that they change that to >4,000 but I don't know why they haven't. Having factual info there is helpful; some people use "not certified" for their own reasons; I guess they don't want direct advice here.

I didn't see anything addressed with regard to free diving during surface interval which (correct me if I am wrong) should not be engaged in as something to do during a surface interval. Snorkeling is ok because you are staying at the surface the entire ime but skin diving (free diving) which is going to depth is a no-no.

It's mentioned here and elsewhere when it comes up, you can look at my first post here altho I did not type it out in detail, but it's often forgotten. I mentioned it to the 2 DMs on a liveaboard once because some were free diving, and they didn't know.