britishtq
Contributor
I need to know as much as I can about bounce diving. Is it safe to do on regular 21% O2? Just throw me some insight.
Bounce diving?
- Thread starter britishtq
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
NO!
Wouldn't a bounce dive include fast ascent rates? Think about it, fast descents which may cause their own complications and then all those dangerous issues you should already know about such as lung over expansion and or getting bent and death in some cases. What exactly did you have in mind? Note the extreme links below:
Blue Hole video or http://www.scubaboard.com/forums/accidents-incidents/173570-holy-s.html Have you seen these?
Hopefully this may change your mind. You work in a dive shop? What do others say at work?
AZ
Wouldn't a bounce dive include fast ascent rates? Think about it, fast descents which may cause their own complications and then all those dangerous issues you should already know about such as lung over expansion and or getting bent and death in some cases. What exactly did you have in mind? Note the extreme links below:
Blue Hole video or http://www.scubaboard.com/forums/accidents-incidents/173570-holy-s.html Have you seen these?
Hopefully this may change your mind. You work in a dive shop? What do others say at work?
AZ
First, let's define a bounce... any dive with a bottom time less than about 10 minutes can be; dives with bottom times less than 5 definitely are. Most bouncers (that I know) use the old Navy table procedure of 60fpm ascent... those tables "allow" bounces (5 min BT) to 190 FSW on air.
It's a fairly common practice in the spearfishing community - arrive at a site, do a rapid descent, have a quick look around, if there's nothing for supper come back up and move on the the next site. It's also common among deckhands who jump in, tie into a site and come right back up.
Is it safe?
In the 160 - 190 ft range the Navy tables require about 6 hours between bounces; at 100 FSW just 10 minutes, but, as the NOAA diving manual says, "In general, experts recommend against this sort of 'bounce' diving, as it may increase the risk of decompression sickness (DCS)." Indeed, the only cases of DCS I know of first hand (save one which was a screw-up on diving the wrong gas) have been after multiple bounces.
My opinion? Bounces in the 100 FSW range with a 30fpm ascent rate and at least a 2 hour SI are probably no more risky than any other NDL dives, but mixing "regular" dives, adding one or more bounces to a repetitive dive sequence usng table calculated SI's, increases DCS risk beyond acceptability. The tables just aren't designed to handle it, and don't do a very good job of it.
Rick
If I recall correctly a bounce dive increases your susceptability to a type 2 hit since you are loading fast neural tissues and not having adequate off gassing. I remember Ted Cole from the WKPP took a nasty spinal cord hit due to a bounce dive.
Why do you ask??
I guess it comes down to what is his specific intent. I would be concerned with extreme ascent rates. I can see Rick's spearfishing example, but what would be the purpose in this case?
AZ
AZ
OP
britishtq
Contributor
One of my friends wants to do it during a trip to Hawaii, I was just concerned for his safety and wanted to know all I can about it, either to feel comfortable with his decision or to talk him out of it. None of the guys I work with know much more about it than I do, so I came here.
But, I thought a bounce dive entailed a fast descent rate, extremely short bottom time, and then a normal "slow" ascent to the surface.
What is a type 2 hit, and how deep can you go and on what mixtures?
Thanks for the help.
But, I thought a bounce dive entailed a fast descent rate, extremely short bottom time, and then a normal "slow" ascent to the surface.
What is a type 2 hit, and how deep can you go and on what mixtures?
Thanks for the help.
That's why it's important to define terms... such a bounce is far less dangerous than a rapid ascent, and, as a single dive it isn't likely to be a problem. Where bouncing gets problematic is when you string them together, especially if they're very deep. The tables (and computer algorithms) just aren't very good models for such diving, and may allow dangerously short surface intervals, so it's best to avoid those allowed short surface intervals.
Deckhands do bounce dives as you define them every day all over the world with no ill effects, but with the following caveats:
1. They are to moderate depths, generally less than 100'
2. They have a decent surface interval - typically at least an hour - between dives. When the tie-ins are deeper, the surface intervals are longer.
A "type 2 hit" is a nerve tissue hit.
How deep? - See my first post in this thread.
How deep on mix? Too deep. See USS Cooper: Return to Ormoc Bay for an extreme example.
** WARNING! If your friend is contemplating something deep, especially if it's deeper than he's been before, then that's an entirely different kettle of fish. If you have the whole profile he has in mind then perhaps you'll get more specific information here. **
Rick
ianr33
Contributor
The internet might not be the best place to learn this stuff. !
A type II hit is an injury to the central nervous system, lungs, or ears. This type of DCS is generally much more serious, long-lasting, and may be at least partially refractory to recompression. There are some who theorize that bounce diving AFTER other dives may compress venous bubbles, allowing them to pass the pulmonary filter, where they then can reexpand on ascent, but now on the arterial side, where they are much more likely to cause damage to the CNS.
Similar threads
