There is a general misconception that good trim means being flat in the water with your feet raised in the “sky diving” position. While this is certainly one part of it, a dogmatic belief that it is the only good position to be in while diving is not beneficial for anyone. Being in the best position for the environment and yourself, by choice rather than by luck is the aim and is GOOD.
While trim usually refers to the diver’s body position and streamlining to their equipment, the two go together. One without the other, undoes much of the good work.
To understand the ideal trim we need to remember its purpose.
Good trim and streamlining help us to:
Move through the water with the least resistance. Swimming is much easier when you are flat, because there is less resistance. So, why do tec divers sometimes ascend in a flat position? There is a hypothesis that this helps off gassing, because our bodies are at the same pressure throughout. While I agree that it is well worth being flat during a deco stop, there are times when I think ascending flat causes more complications than it has potential benefits. Communication with buddies can be more difficult and it can be harder to exhaust gas from drysuits. While I don’t think there is any need to be completely vertical, tilting your “sky diver position” a few degrees to vent gas or signal your buddy is better than a rapid ascent or lack of communication.
Avoid disturbance or damage to the environment. In a cave environment this can mean distorting your body into various positions to keep your feet away from silt (which can be on walls and ceilings as well as the floor) and twisty turn passages needs lots of changes to body position to keep good trim. More commonly we respond to the marine or lake landscape, which is less extreme. Descending down a slope in a horizontal position can result in trailing fins, if we do not adjust our body position. The diver’s body needs to be at a similar angle to the slope (or a greater distance from it) to avoid problems. By the same token, if you are hovering over a drop off hundreds of metres deep and fancy tipping your body up to take a photo – no probs – you’re not going to kick anything.
Be in control. This is the key for me, the diver should choose their position based on where they are and what they are doing. Returning to the default flat position, where it easiest to swim horizontally, in between. Trim should not be compromised by lack of buoyancy control, but new equipment may require a period of adjustment to regain your normal trim, streamlining and control.
Of course, if you or your students are swimming around kicking up the vis and/or damaging the environment that is BAD – ‘nough said.
So what is the really UGLY? I have recently started to see and hear divers talking who feel so pressurized into being flat in the water that they prioritise it to the detriment of everything else. Just one example, was a newish diver on a workshop recently. She had yet to really master buoyancy control in her new drysuit, but unfortunately, she had been led to believe that being flat in the water was the most important thing. This caused massive physical struggles and significant frustration for her, because she couldn’t control her buoyancy well yet, so everytime she tried to get flat in her drysuit and ascend the air went to her feet and she lost control. We discussed it afterwards. her weighting was good and her equipment well streamlined and balanced, so I suggested practising hovering and ascending without worrying about body position, then progressing to controlling body position. Unfortunately, she had been so indoctrinated by a more experienced tec diving partner that she believed good trim was more important than good buoyancy control….
I’m not saying new divers can’t learn buoyancy control and body position at the same time, that is certainly the ideal, but if that isn’t working, like any skill, it may need to be split into smaller sections to achieve mastery and some divers may take longer than others to put it all together.
Personally, I think buoyancy control is always the most important skill and the foundation for others. Not only does this example underline that importance, but it also highlights the need to build confidence and to allow newer divers to progress at their own pace, not push our tec diving expectations onto them. I firmly believe this diver would have done better if she had been told to aim for good trim, but not worry if it took a while to get it right. Instead she was convinced that being anything other than horizontal was a mortal sin.
Good buoyancy control, equipment streamlining and weighting allow you to change positions underwater at will, not be pinned in a particular attitude by your kit or lack of buoyancy control. The freedom to choose the best position for the situation you are in is my definition of good trim.