Holding a safety stop - the effect of breathing/weighting

[Lorenzoid]

Thanks all - perhaps I'm reading too much into the 'deep' breathing. . . .

What is considered an acceptable fluctuation from a stop depth due to breathing? 0.5m either side? Can you ultimately get to a point where you don't move at all?

It's common to see advice to breathe "deeply," but it's simply a matter of poor wording. Breathing shallowly during a dive is bad, as it can cause you to retain CO2, potentially resulting in headaches among other problems. (Whether it affects offgassing seems dubious--if I recall, that has been discussed on SB and debunked.) Advice to breathe "deeply" is intended as a way to emphasize "not shallowly." The best advice I received is what others here have said: take normal, full breaths, whether at a safety stop or any other point in a dive. It helps the body properly exchange gases and helps with depth control.

You should rise and fall almost imperceptibly with each inhalation and exhalation. Just a few inches each side--so little that if you're watching some floating particle you can keep your eye on it the whole time, watching it seemingly bob up and down. (That's actually a great way to practice.)

Holding a stop in shallow water is one of the hardest skills to master. I thought I had gotten good at it after all my years diving a tropical rig, and then when I started diving a steel twinset I realized I hadn't mastered it at all and spent several more years working on it on a regular basis. The more massive the tanks, the more it's important to keep your depth under control. Once you lose control and begin inadvertently ascending or descending, you have to fight the momentum of the tanks to arrest the ascent or descent.

 

[johndiver999]

How about.. hold onto the anchor line or.... Wear a little more lead, deploy an smb from 20 feet and then hang down on it. This will prevent you from moving up and down,

If you want to practice, let go of the reel//spool and keep the spool right in front of your eyes. You should be able to train yourself to avoid bouncing around so much. After you get better at it (as mentioned above) looking at the particles in the water works pretty well.

 

[Hartattack]

Since the breathing aspect of the conversation has been well handled by all. Let's talk about the concept of a balanced rig or balancing out the equipment you carry. As one moves into more of a technical diving profile (also works well in rec) the need for a 3 minute stop at 15 feet decreases and a different minimum decompression and ascent plan emerges depending on the agency you move forward with.

With that said, what seems to be a constant is the ability to have a well balanced gear configuration that you would have the ability to "swim up" from max depth due to a loss of buoyancy (adding gas to the wing or drysuit) emergency, and the ability to hold a 10 foot decompression stop with near empty tanks.

The way to achieve this is to of course practice your weighting and in-water skills, buoyancy, trim etc. However, changing up you configuration of gear adds to this a bunch.

My recommendation would be to trade in that jacket style bcd for a Back Plate and Wing—you are already talking about Tech dives, might as well get the correct tool needed for the job. The Backplate can be made of many materials, but the ones that can help in the weight department would be the stainless steel and aluminum type. Most folks dive a SS BP with ALU tanks and vise versa for Steel tanks.

E.g. My normal rig is double LP 85 steel tanks, ALU BP, 45 pounds of lift wing, 2 1/2 pounds V-weight (positioned center line between the tanks) a cannister light and dry suit.

Thant's it, no extra weight belt, no detachable weights, etc. because that's what works for me to swim up from max depth in case of an emergency and I can also hold a 10 ft stop in trim, relaxed with near empty tanks.

Here are two videos and some links from different agencies explaining the concept. the videos are a bit old, but good gouge nonetheless:

GUE/GI3

ISE

Equipment considerations

Equipment List

I hope this helps you on you journey. Cheers.

 

[boulderjohn]

I would think that a greater rate of breathing, within reason, would have a larger affect on N2 off-gassing than larger volume breaths.

I just want to make this point as clearly as possible, since this issue comes up from time to time on ScubaBoard. It seems logical that the rate at which we breathe would have an effect upon both on-gassing and off-gassing. If you are incredibly bored and have loads of extra time due to Covid-19, you could even find a thread I started asking about this 14-15 years ago. In one thread a few years later, a quite famous diver was quite insulting to all those who did not agree with him that breathing rate affects on-gassing and off-gassing.

It turns out, though, that breathing rate has no effect on either on-gassing or off-gassing. If you do find that thread I started so many years ago, you will find that the question was answered that way quite tersely by the man who went by Doctor Deco on ScubaBoard back then--Michael Powell, who was then one of the world's foremost experts on decompression theory.

 

[OTF]

I think it's also important to explain why that is. In a simplified sentence: offgassing is controlled by the rate of inert gas diffusion out of tissues based on saturation and ambient pressure, not the rate of gas going in an out of your lungs.

 

[Storker]

Free hovering a stop without a visual reference is HARD in the beginning.

FTFY

 

[Storker]

Keep working on reducing the amount of weight that you carry.

There is a thing called "not enough weight". Don't reduce the amount beyond what you need. IMO struggling to keep the safety stop sucks majorly, having a few hundred grams too much weight so you have to have a couple hundred mL of air in your wing... sucks not so much, IMNSHO.

 

[ross9]

Is your BCD completely empty of air at your safety stop?

Yes, I've emptied all my air from the BCD at the safety stop. In the OP when I said I'm adding less air to my BCD, I meant at depth i.e. as a result of getting better at taking a little less weight on the dive.

My recommendation would be to trade in that jacket style bcd for a Back Plate and Wing—you are already talking about Tech dives, might as well get the correct tool needed for the job. The Backplate can be made of many materials, but the ones that can help in the weight department would be the stainless steel and aluminum type. Most folks dive a SS BP with ALU tanks and vise versa for Steel tanks.

This is a debate I'm having at the moment. I'm still renting BCDs but planning to get my own gear - haven't decided between BCD or BPW yet. I can see the advantages of BPW, I've just never dived with one. So would like to give one a go before I invest in my own.

 

[ross9]

If you want to practice, let go of the reel//spool and keep the spool right in front of your eyes. You should be able to train yourself to avoid bouncing around so much. After you get better at it (as mentioned above) looking at the particles in the water works pretty well.

This is another good idea - I shall give this a go too. Thanks

 

[OTF]

If you're diving frequently/locally it REALLY makes sense to own gear ASAP rather than rent. Do the math.