safety stop?

[midwestdvr]

Okay, this might seem like a stupid thing but I don't think I've ever done a safety stop. My OW cert and immediate post cert dives were done at the inner reefs in Key West where I barely went deeper than 35 feet. Most of the time was done in 25feet or shallower. On my recent trip to the philippines, I did beach entries and the dives were on a slope so dove deep on the first half and on the return trip progressively went shallower along the slope then surfaced. During all these, probably spent the last ten minutes of the dive in 20 feet or less. Now, what worries me is that I'm planning to go back to the Keys later in the spring and I fear that I will have to do a safety stop where you actually do stop at the proper depth on the way back to the boat. Any tips or pointers on proper way to do this? Thanks.

midwestdvr

 

[Scubakevdm]

Hello MidWest diver, I hope I can help you out a little with this. First of all, don't get too upset about not doing a safety stop, it's a good idea... maybe a very good idea to do 3 minute stop at 15 feet for a number of reasons, however a safety stop is not a decompression obligation. Safety stops are pretty handy for not getting run over by boats, having more control over the most critical part of your ascent, and the just to be safe decompression angle is there too. Safety stops require a certain amount of practice with buoyancy control, and I don't know exactly where you stand with that, but if you are still honing your bouyancy control skills, maybe its a good idea to try to be slightly negative throughout your ascent and kinda kick up a little. Remember that any air that is in your BCD will be expanding quite a bit as you approach the surface, and will require periodic venting. There's probably more too, and maybe I'm not the mac-daddy safety stop knowlege guru, but that's a start. We recommend our divers make safety stops, and do our best to facilitate them, but not everyone is able to pull them off. Don't feel to bad if you blow past them at first, but do keep trying, you'll get the hang of them. Peace, -Kev

 

[Scubakevdm]

P.S. If you want to practice them on your way down to the Keys, make a couple of dives with us and I'll help you out.

 

[scubafool]

Most of the charter boats I've dove off of here in FL usually tie off to a buoy or the wreck when diving at a fixed location, so you have that line to hang on to while doing you're doing your stop. On drift dives, however, you don't have that luxury, & holding a good stop can be difficult if you don't have good bouyancy control. One thing I've seen done & I believe I've seen it mentioned on this board, is to deploy a lift bag & hang on the line from that to complete the stop. However, deploying a lift bag seems to have safety considerations that I don't have the knowledge to comment on, so be sure that you know what you're doing before you go that route. And hey, good bouyancy skills make diving so much more fun anyway. Also, this may seem basic & unworthy of mention, but I'm gonna say it anyway. Make sure you depart the bottom with plenty of gas for the stop & a comfortable reserve. Hey you can always hang around at your stop longer if you just can't stand getting back on the boat with 800lbs left. Also probably basic but worth mentioning is ascent rate. The slower the better. Enjoy diving this great state, & if you want to get in some diving off of the beaten path, myself or other SB members around here can give you plenty of ideas. Cheers!

 

[MXGratefulDiver]

Okay, this might seem like a stupid thing but I don't think I've ever done a safety stop. My OW cert and immediate post cert dives were done at the inner reefs in Key West where I barely went deeper than 35 feet. Most of the time was done in 25feet or shallower. On my recent trip to the philippines, I did beach entries and the dives were on a slope so dove deep on the first half and on the return trip progressively went shallower along the slope then surfaced. During all these, probably spent the last ten minutes of the dive in 20 feet or less. Now, what worries me is that I'm planning to go back to the Keys later in the spring and I fear that I will have to do a safety stop where you actually do stop at the proper depth on the way back to the boat. Any tips or pointers on proper way to do this? Thanks.

midwestdvr

Doing mid-water safety stops requires good buoyancy control and practice. So my first bit of advice is to practice it in "ideal" conditions first ... i.e. someplace with decent vis and no current. Start with a relatively shallow ascent ... say from 30 feet or so. As you ascend, try to come up as slowly as you can and make frequent stops (every 5 to 10 feet) for at least 10 seconds ... trying to hold your depth at each stop.

On your shore dives, practice holding a hover with no fin (or hand sculling) movement at 15 feet. To get a better "feel" for what a mid-water ascent might be like, practice this a few feet off the bottom. Just try to hold still for a minute or so without rising or sinking.

Remember that if you're fairly close to neutral you can control your depth with your breathing. Practice this at depth first, since the closer you get to the surface the more affect the air volume in your lungs will have on your buoyancy.

Should all else fail, remember that it's easier to hold a given depth while moving than while stationary. A safety stop can be done easily by swimming around at depth than by hovering. It's not good form, but it's better than blowing one if you should need it.

Above all else, you should understand why safety-stops are recommended in the first place. Whenever you come up from depth, the nitrogen coming out of solution in your body tissues (due to depth changes) will cause bubbles to form in your blood. You can minimize the formation of those bubbles by coming up very slowly, but you will not prevent them altogether. The safety-stop is just a precaution to help your body absorb those and pass them out thru your lung tissues. While it's not a requirement for non-deco dives, it does minimize the risk of excessive bubble formation (which varies depending on the dive profile and your particular physiology on a given day) and reduces DCS risks ... as well as the fatigue you'll feel after a dive due to nitrogen loading.

Given that knowledge, realize that it's far more important to come up slowly than it is to actually stop at 15 feet. While the purpose of the safety stop is to let the nitrogen bubbles in your blood dissipate, coming up really slow (like 10 feet per minute) will help prevent them from building up in the first place.

... Bob (Grateful Diver)

 

[dbulmer]

Just an extra point to add to the comments above.

If you can get some practice in a swimming pool that'll help. Also don't let it be a worry. If you have had a good dive you won't be in a hurry to get out of the water anyway (of course keep an eye on your gauges!) so take your time and come up real slow as NWGratefulDiver says.

On some dives you'll come up on a line as was said earlier, consider it part of the dive.
When I am on a line, I usually check my gauges and think of all the poor people in my workplace that are at work - brings real tears of joy!

 

[ColdH2Odvr]

Ditto what Bob said +

Here’s a quick look at why the safety stop can be a good thing. This chart shows the Doppler bubble count for three dives. All three are 120’ for 25 minutes. The top line has no safety stop, the second has 2 min at 10’ and the third is 1 min at 20 feet, 4 min at 10.

http://www.rockisland.com/~dgrove/VGE_Bubbles.jpg

This graph was pulled from Technical Diving in Depth by Bruce Wienke. I have no idea what the test conditions were, number of samples taken, the order of dives etc. but it’s defiantly good food for thought.

Also, a silent or hidden stop (chillin at the surface for a few minutes) is annother good way to get the bubbles out gently.

Have fun in the Keys!

Dave

 

[DA Aquamaster]

A good landing in a plane starts with a smooth approach. Same thing with a good saftey stop.

Start with a slow ascent rate (30 fpm) and begin to slow this even more as you pass 30 ft on your way to the 15 ft stop. It almost always helps to dump air from the BC with the goal of staying neutral or even slightly negative and finnng your way up rather than trying to ride the BC up. If you are riding the BC, that last 30 feet can easily get out of control as the expansion ratio of the air in the BC is much greater than at deeper depths.

A slow ascent under fin power leaves you in an exceellent position to halt the ascent and establish neutral bouyancy at the 15 ft mark.

 

[simbrooks]

We had similar troubles on our first ocean drift dives in midwater. Couldnt see the bottom, had no other references to judge depth by apart from guages. Due to this our safety stop was somewhere between 10-20ft for about 5 mins, so although the time was ok, the depth control and lack of reference was a bit of a pain (i realise now i can look at the stuff in the water - after reading on here or ditching a SMB - need to work on that one!) and something we have to work on!! Most other diving is in springs and the like, where references are all around, much easier to hold a stop within 1 ft of 15ft like that!!

Hope you get it sorted out midwest, we are planning more drifting dives off SE FL in the coming month or so -would have gone last weekend IF it werent for my cold, grrr that was frustrating to cancel that trip.

 

[Scubakevdm]

We had similar troubles on our first ocean drift dives in midwater. Couldnt see the bottom, had no other references to judge depth by apart from guages. Due to this our safety stop was somewhere between 10-20ft for about 5 mins, so although the time was ok, the depth control and lack of reference was a bit of a pain (i realise now i can look at the stuff in the water - after reading on here or ditching a SMB - need to work on that one!) and something we have to work on!! Most other diving is in springs and the like, where references are all around, much easier to hold a stop within 1 ft of 15ft like that!!

Hope you get it sorted out midwest, we are planning more drifting dives off SE FL in the coming month or so -would have gone last weekend IF it werent for my cold, grrr that was frustrating to cancel that trip.

Eventually, you will be able to feel whether you're ascending, descending or neutral (especially if you own your own BC, you get to know it better than going from rental to rental). You can fine tune your bouyancy with the depth of your breathing. This takes practice, and is not something you should only be doing on your safety stops. It is the mastery of bouyancy control period. It just becomes more critical and more difficult at shallower depths because air expands and compresses more up there, so you have to kinda be on it more up there. Alot of old timers take their safety stops at 20' because its a little more stable down there.