All the Trimmings

Remember when your Open Water instructor just kept loading weights into your BC until you could float at eye-level? Do you remember that you almost certainly still had a bunch of air in your BC because you weren’t yet proficient with the device? Do you remember that you were probably unconsciously still kicking to keep yourself on the surface because your reptilian brain was fleeing the feeling of drowning? Of course I’m not talking about you, specifically. I’m sure you took to diving like the eponymic fish to water. I’m talking about the hundreds and hundreds of other people who definitely weren’t you who demonstrated this behaviour over my years teaching open water classes. No kidding, I was wearing about 40lbs when I did my first day of check-out dives in a 7mm off the coast of Puerto Vallarta. That day was a shit-show for a lot of reasons, the crap weighting just one of many. That is repeated day after day year after year all over the world. On a dive boat right now somewhere in the world the DM is calling up to the deck for more weight because someone already wearing an actual anvil on their belt still can’t descend. This is, of course, a stage most people who start finding their way into the tech diving realm discover how to leave behind. They start to shed weight and begin to take pride in just how little they wear. Frequently divers will go a little too far with this, dropping 2lbs too much and finding themselves struggling to maintain a safety (or worse… a deco) stop. And so, with hearts heavy with remorse, they put the 2lbs back to be worn forever in shame and ignominy like a scarlet A. Which is flawed thinking, too. And what I’ve noticed leads some of the folks I work with struggle to wrap their head around. The difference and necessity of trim weights in addition to ballast. Let’s define ballast as what you need to actually descend. A good actual Open Water weight check would be when a tank is down to 500psi, the BC completely empty, and at 15 feet of depth the diver can hover motionless. The eye level thing… absolute hogwash. And the principle holds true through any level of diving. Can you maintain depth with empty gas spaces and nearly empty tanks? Trim weights are something that, as a diver, you’ve heard of. Even most recreational BCs have trim weight pockets nowadays. They’re used as a way to reposition your centre of ballast (against your centre of buoyancy) so that you can maintain the flat, hydrodynamic rockstar diving position. Here’s the moment that I get looks of bewilderment: ballast can be trim, but trim doesn’t have to be ballast, you might need to be overweighted. There are only so many places you can place trim weights. That is, it’s all well and good if you know that you need exactly 10lbs in a certain spot, but the physical limitations of the space might not allow for that much weight in that spot. What winds up happening is that you need to distribute the 10lbs you need as ballast up and down your back, but now your trim is all jacked up. So you need to add another 2 or 4 or however many lbs somewhere or another to correct it. Yes, now you’re overweighted. And your vanity is struggling agains years of thinking, “The less weight I wear, the awesomer I am!” But you’re actually set up to be properly balanced and stable for the entirety of the dive. I’m obviously not suggesting that anyone anywhere actually needs 40lbs. Just that a two pounder or an extra v-weight here or there can make a surprisingly big difference. People tend to grow pretty happy with the concept after a dive or two of being able to maintain flat stability without having to even think about it too much. So you might consider swallowing pride, allow yourself to be slightly overweighted, and get comfy. Or let your precise ballast drag you into whatever position it seeks as equilibrium against your buoyancy and try to swim around like that. Why should I care if you prefer to make life harder on yourself?