So how do you teach your new OW students the relationship between weighting, buoyancy, and trim?
I'm not a certified instructor; however, I view them as separate but tiered concepts, and the order of understanding is important. Of critical importance, though, is to eliminate the masking effect of propulsion. (I'm assuming a drysuit is NOT involved in any of this, BTW.)
- Proper weighting can be directly measured without kicking.
- After being weighted correctly, neutral buoyancy can be taught by not kicking. As much flack as the Budda hover gets (or whatever position your body happens to take with legs crossed to prevent kicking), it makes it very obvious that you understand neutral buoyancy when normal breathing has you hanging mid-water in the pool. This includes balancing the air distribution between BC and lungs to achieve that "normal" breathing range. This has little to do with "proper" weighting, requiring only that one is weighted "enough". (Granted, it's easier when properly weighted because buoyancy changes are slower, giving one time to sense/react.)
- Finally, the distribution of the weight is adjusted so that rotation is eliminated when physically placed in the desired horizontal trim position by an instructor. Yes, there's discussion about what muscles need to be contracted, core stabilized, head up, torso/knees straight line, etc., but if someone hasn't moved a muscle and rotates fairly quickly when released, that clearly points to weight distribution. Nothing to do with total weight or buoyancy. Once weights are close to correctly positioned, the rotation when released will be slow and can be controlled (either direction) with small positional changes of legs/hands.
If everything is free to be adjusted at once, it's very easy for seahorse trim + kicking + negatively buoyant to perfectly balance out and yield horizontal movement at a constant depth. Indeed, people who care about the reef can make themselves slightly positively buoyant + slightly head down + kicking yielding horizontal movement inches above the reef. (Believe me, when sharp urchins abound where you dive, you quickly learn to respect them!)
Again, this is just how I view things. My OW class (NAUI, late 80s) never even talked about "trim". Hundreds of dives and I never kicked the reef, so I thought I was great. It wasn't until I saw video of myself years later that I realized I was in the slightly kicking down category.
TLDR; My buoyancy control was great, but I was cheating by using propulsion to maintain trim. My opinion is teaching weighting, buoyancy, and trim as separate concepts without the masking effect of propulsion will sort someone out pretty quickly. I know it did for me.