Are trim and buoyancy fundamentally related?

[boulderjohn]

Back when I was teaching I often would have someone ask to take a photography class. Most went elsewhere after I explained to them that my photography class was going to put as much emphasis on their diving skills as it did their photography ... because you can't get good pictures without good diving skills ...

When I dived in Puerto Galera, Philippines, on every dive we had at least one diver, and usually more, withe a huge camera setup. They invariably carried reef sticks, long metal pokers designed to allow the diver to hold position while taking a shot. I had the same DM on every dive. After a few dives, we were alone on shore and I said that from what I had seen so far, the true purpose of the reef stick was to allow the diver to take pictures while negatively buoyant and no longer able to maintain depth by kicking. He shook his head in disgust and said "90% of them." That was after a dive in which he went behind a diver who was taking a picture and held the diver's feet up so he would stop smashing them on the coral while supporting the upper part of his body with the reef stick.

When I arrived at that resort, I had to join a group of other new arrivals to watch a film on how to take pictures with proper buoyancy so as not to destroy the reef. It did not seem to do much good.

So, you can get good pictures without good diving skills, as long as you don't care how much damage you are doing as you get them.

​

 

[HantsDiver]

The standards for the dive specify, as you noted in the first sentence, above, that the student should not 'lose control of buoyancy, body position or depth' (my formatting, added for emphasis). That is different from what you say in your second sentence, 'your students are doing this without a change in body position'. I can doff and don in mid-water and not 'lose control of buoyancy, body position or depth'. My OW students, before they can be certified, can doff-and don in mid water and not 'lose control of buoyancy, body position or depth'.

Yes, it does. 'Remove, replace, adjust and secure all or part of the weight system without losing control of buoyancy, body position and depth. • With weight belt and weight integrated BCD – on the bottom in water too deep in which to stand.' (My formatting added, again, for emphasis.) I regularly violate this 'standard' during Confined Water training, as I require students to do this mid-water / neutrally buoyant.

If you can make it work for you then great. I think there are safer ways of dealing with the incredibly rare event of something snagging you from behind. I'm less than convinced that the students will truly be in control of their body position and depth. If I'm in control of my depth is doesn't change if I don't want it to. Same goes for body position.

Rather than routinely violate standards - why not just ask for a standards exemption from padi? I might be the only one who can - but I think it's there for a very good reason. But you might be able to get padi to agree to it. If an instructor was suggesting they were taking OW students to 25m or violating other standards it wouldn't be accepted. If a student were to complain how would you justify it without an exemption?

There is another reason I'm not a fan of this sort of stuff. What is going to happen if the student tries this before they know better in a semi dry and a wing or integrated weights? When/if they do try it to fix a problem rather than using their buddy at 30m and end up with no gas supply are you not going to feel a little bit responsible?

 

[HantsDiver]

I would think if you are entangled it would be tough to descend to the bottom before getting out of your Bcd/Bpw.

How tough would it be to signal to your buddy? Or for him/her to help you?

We can come up with lottery odds scenarios - like losing the buddy and then becomming stranded in fishing line. But the reality is your time is better spent learning to work as a team rather than doing daft things like taking off your wing underwater.

 

[Clark Fletcher]

Just my humble opinion but, I'd say that buoyancy and trim are NOT fundamentally related to each other.

I say that because each can exist independently of the other. You can have decent buoyancy control and really crappy trim. And, you can have pretty decent trim and extremely crappy buoyancy control. As a recent returnee to diving after a long absence, I have experienced both of these situations.

What I would say is that BOTH trim and buoyancy are fundamentally related to the best possible diving experience. If you are properly trimmed and have good buoyancy control, you can pay less attention to constantly adjusting things and more time enjoying your surroundings. And, you expend less energy moving through the water and use less air doing so.

Admittedly, having a handle on each may make getting a handle on the other a bit easier but again, I wouldn't say that they are fundamentally related.

 

[boulderjohn]

What has happened is that buoyancy and trim have been mixed in scuba thinking to include both, even though they are technically separate skills.

I established a buoyancy and trim workshop when joining a new shop. I wrote up a brief description for the shop's newsletter, which the owner then published. He made a title that focused on advanced buoyancy control, and he wanted to jazz it up with a picture. He chose a stock photo to dominate the newsletter, a photo of a diver doing the Buddha hover, with the body perfectly vertical. When I saw it, I told him that anyone interested in learning advanced buoyancy and trim and who knew what that meant would look at that photo and dismiss the workshop without bothering to read the description. I later talked with others who said exactly that--they saw the photo, figured it was the same old BS, and didn't bother to read.

 

[MXGratefulDiver]

When I dived in Puerto Galera, Philippines, on every dive we had at least one diver, and usually more, withe a huge camera setup. They invariably carried reef sticks, long metal pokers designed to allow the diver to hold position while taking a shot. I had the same DM on every dive. After a few dives, we were alone on shore and I said that from what I had seen so far, the true purpose of the reef stick was to allow the diver to take pictures while negatively buoyant and no longer able to maintain depth by kicking. He shook his head in disgust and said "90% of them." That was after a dive in which he went behind a diver who was taking a picture and held the diver's feet up so he would stop smashing them on the coral while supporting the upper part of his body with the reef stick.

When I arrived at that resort, I had to join a group of other new arrivals to watch a film on how to take pictures with proper buoyancy so as not to destroy the reef. It did not seem to do much good.

So, you can get good pictures without good diving skills, as long as you don't care how much damage you are doing as you get them.

​

Can't do that where I normally dive, because touching the bottom blows out the vis. Some places you can do that without even touching the bottom ... all it takes is moving your fins while trying to hold position. If you want decent shots, you have to learn how to position yourself and hold that position for long enough to frame the shot without moving. That often requires you to get above the subject, breathe out enough to sink, breathe in enough to regain neutrality, and then hold it long enough to take the picture. It's not really as difficult as it might sound ... it just takes a bit of practice.

... Bob (Grateful Diver)

 

[MichaelMc]

On being interrelated, you have to talk about depth and kicking, as they are the major reasons we care about buoyancy and trim. If stationary and neutral, buoyancy and trim interact minimally; if stationary and negative, you must be vertical and kicking to stay stationary. If kicking, 45 degree or vertical trim will change your depth, your suit or BC squeeze, and thus your buoyancy, unless you are negative. That sounds really related to me. Horizontal trim has an effect of separating buoyancy and trim from depth while kicking, as long as you stay horizontal...

On teaching mid water ditch and don, it is best when buddies are not dependent on each other, but enhanced and pay attention. An extreme version of ‘my buddy can fix that for me’ is not worrying about reaching your valves to do a shutdown in doubles as your buddy can do that for you. I do not think you would advocate that. I do not think it is a good idea to leave divers dependent on their buddy for things they can solve with a drill that enhances their water skills. Mid water ditch and don enhances diver self reliance and is a good exercise in controlling yourself in the water while messing with major parts of your dive system, sounds win win. Not teaching it because they might use when their great buddy is next to them sounds like not teaching CESA because they might do it instead of asking their buddy for air.

If your objection is on priority in training, being a good assistant/safety diver while you buddy practices sounds like good team training. If your water skills are good, its not hard or time consuming. If they are not good, its really hard, time consuming and a good time for your buddy to be watching you in class... win win.

 

[HantsDiver]

On teaching mid water ditch and don, it is best when buddies are not dependent on each other, but enhanced and pay attention. An extreme version of ‘my buddy can fix that for me’ is not worrying about reaching your valves to do a shutdown in doubles as your buddy can do that for you. I do not think you would advocate that. I do not think it is a good idea to leave divers dependent on their buddy for things they can solve with a drill that enhances their water skills. Mid water ditch and don enhances diver self reliance and is a good exercise in controlling yourself in the water while messing with major parts of your dive system, sounds win win. Not teaching it because they might use when their great buddy is next to them sounds like not teaching CESA because they might do it instead of asking their buddy for air.

What sort of diving do you do? On a serious dive there are a number of things that not only can cause problems which are realistic, which I simply could not solve on my own. If I lose my deco gas I'm in big trouble. The answer is not to carry twice as many deco tins but to work better as a team.

Have you ever dived in a steel twinset, with a steel backplate and a tail weight and with a drysuit? Have you ever dived with stages or deco tins? Have you ever dived with a scooter? Do you think you can control all these things whilst messing around with your wing off?

In solo diving it might be appropriate. I say might as anyone with a brain would make themselves negative and hold onto whatever was causing the problem so their bcd could not fly away. What's more - removing yourself from your bcd/wing will be rather different if it's trapped anyway won't it. Rather than moving the equipment you will be moving yourself. So the value of the skill is not only questionable - it's useless.

 

[MichaelMc]

What sort of diving do you do? On a serious dive there are a number of things that not only can cause problems which are realistic, which I simply could not solve on my own. If I lose my deco gas I'm in big trouble. The answer is not to carry twice as many deco tins but to work better as a team.

Have you ever dived in a steel twinset, with a steel backplate and a tail weight and with a drysuit? Have you ever dived with stages or deco tins? Have you ever dived with a scooter? Do you think you can control all these things whilst messing around with your wing off?

In solo diving it might be appropriate. I say might as anyone with a brain would make themselves negative and hold onto whatever was causing the problem so their bcd could not fly away. What's more - removing yourself from your bcd/wing will be rather different if it's trapped anyway won't it. Rather than moving the equipment you will be moving yourself. So the value of the skill is not only questionable - it's useless.

We are not talking technical dive training here. If we were, wouldn't you like them to have gotten the water skills that allow a mid water single tank ditch and don early on? Air is the big redundancy we depend on a buddy for, but we plan for CESA as a contingency.

I dive low vis northern California kelp forest with a single tank back plate long hose 20/10mm wetsuit while shepherding pairs of advanced students focused on counting stuff underwater. I'm bordering on being solo and my wetsuit has a lot of lift. Taking off my rig is not to be taken lightly, even without additional equipment. I've done ditch and don in that 20/10 mm in the pool at 8', though on the bottom, complete ditch/don, weight belt, mask, fins, reg, everything save the wetsuit and booties. Securing all the ditched gear to the rig as one package. I've done the same, except the weight belt, midwater at 6' easily in a 10/5 mm, while maintaining horizontal trim in formation with two dive buddies. We do not require it but many of our students do it in the pool mid water just fine in 7mm, some in backplates.

How do you propose our divers make themselves negative when half their considerable lead in on their rig? If it's really hard wrapped in kelp/line, what if we practice it in the pool first to give us a head start?

The BC only version is an easy drill and test, if they have good water skills. Do you object to requiring them to have good water skills? Do you object to using it as a test of good water skills?

 

[HantsDiver]

We are not talking technical dive training here. If we were, wouldn't you like them to have gotten the water skills that allow a mid water single tank ditch and don early on? Air is the big redundancy we depend on a buddy for, but we plan for CESA as a contingency.

I dive low vis northern California kelp forest with a single tank back plate long hose 20/10mm wetsuit while shepherding pairs of advanced students focused on counting stuff underwater. So I'm bordering on being solo. My wetsuit has a lot of lift. Taking off my rig is not to be taken lightly, even without additional equipment. I've done ditch and don in that 10/20 mm in the pool at 8', though on the bottom, complete ditch/don, weight belt, mask, fins, reg, everything save the wetsuit and booties. I've done the same, except the weight belt, midwater at 6' easily in a 10/5 mm, while maintaining horizontal trim in formation with two dive buddies. We do not require it but many of our students do it in the pool mid water just fine in 7mm, some in backplates.

How do you propose our divers make themselves negative when half their considerable lead in on their rig? If it's really hard wrapped in kelp/line, what if we practice it in the pool first to give us a head start?

The BC only version is an easy drill and test, if they have good water skills. Do you object to requiring them to have good water skills? Do you object to using it as a test of good water skills?

Bold bit's in order.

How does taking off your equipment give you water skills? What skills does it give you? If it gave good skills tdi/iantd/tec-rec etc would introduce it. They don't because it doesn't prove or teach anything useful.

CESA is there as a last chance backup as people do not last very long if their buddy is even a few seconds away. It's only meant to be done in shallow water.

They can make themselves negative by changing their configuration or more simply by leaving their equipment on. There is no need to take it off lol.

I do object to using it as a test of good water skills... As it doesn't test anything to do with good water skills. It's ridiculous. If I or anyone I know were diving and saw people doing this we'd spit our regs out from laughing after we were sure they were okay. After that we'd video it and share it with others. There was an old name for people who did this "stroke" - this is totally stroke like behavior.

Edit - why don't you get a drysuit??? and what is a dm candidate doing guiding people around?