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Lower the Lead

Just as often as not the first day or two of just about any class I have the same back and forth with students: I try to persuade them that they are actually head heavy - they tell me all the reasons I’m wrong. Some folks - usually the ones who spend a lot of time at the gym getting jacked - don’t even really need ballast… but do need at least one trim weight to correct their head-heaviness. But don’t want to because there’s some sort of point of pride in not wearing any weight. Most people agree to play along with my preposterous theory by the afternoon of day one. These people tend to have the most productive consequent days as they find themselves suddenly balanced and stable, allowing them to focus their attention on learning whatever new tasks and skills they’re here to learn. Rarely it’s by day two or three when (super-weirdly) they realise that they are, indeed, head heavy and they need to wear weight much lower. And, from then on, we do not speak of it anymore. I’m not exactly an “I told you so,” kind of person. (Besides, they already know that I most certainly did.)

This is obviously what we want to look like. Or near-enough like. Broadly speaking, since we do not want to be made of wood like Scubanocchio here. Buoyancy and ballast perfectly balanced so that we are truly neutral in the water. With that balance at a centerpoint that naturally places a diver at rest in 0° trim. It’s an unnatural position, obviously. Trying to gently arch your lower back and look directly overhead for long durations isn’t really what our physiology is equipped for. Either one of those things can pretty easily lead to a major muscle stitch that could take a few days to work out. (Which is one of the reasons why I always ask people what their longest duration of dive is. Everyone thinks they want to be in the water for 5 hours straight. But, trust me, you probably don’t.) Not only is it an unnatural position, but there are a LOT of different forces at play to achieve it.

{NOTE: Most of the rest of this post is quite Mexico-centric. Here AL80s are almost universally the tank of choice; 80s work funny. They’re slightly negative at the beginning of the dive and can be quite positive by the end of the dive. And that floatiness comes from the base of the tank which has become an aluminium ballon. This is why the tank buoyancy in the above illustration is marked “variable.” In Florida 80s are almost never used as backgas, with higher volume steels much more favoured. Those tanks are just anchors from beginning to end and, as such, weight (which is what most of this post is about) is only rarely even worn.} {ANOTHER NOTE: This is also sort of focused on backmount, but many if not all these principles can be applied to sidemount as well. On sidemount, in fact, the idea below of changing one’s fulcrum around is even more critical, given the variability of buoyancy of the tanks is even further away from the diver’s center-mass. You’ll see what I’m talking about in just a moment.} Obviously the biggest and most easily variable of the balance are the placement of where all the heavy brass - the heaviest parts of the tank - is placed, how much air is in the wing, and how much weight is worn and where. With fin selection running pretty close behind. All the brass: How high do you wear your tanks? This can be adjusted by sizing the harness correctly and/or choice of bolt-holes in a plate. Also, as far as brass is concerned, are you still using Zeagle Flathead 7s that weigh as much as a VW Bug each? Why? Get new regs. Something with a swivel preferably. The wing: Think of it as a cute, fluffy taco that is giving your tanks a hug. The air should be on either side of the tanks. Not all bunched up behind your head like a travel pillow that makes it hard to reach your valves. Skipping ahead, fin selection: It’s the rare diver in tech gear that doesn’t benefit from a set of dense, heavy fins. Personally, I’ve had several students for whom I’ve brought a pair of Jets along for a day, “Just in case.” Most folks resign themselves to needing to rent them for the week or that they’re buying new fins. Once had a student whose first words, on surfacing from a dive, where “Can we stop someplace so I can buy a pair of these on the way home?”

Something that is not only more sensible than ankle weights in literally every single way in the whole entire world. But can be moved closer to and further away from the body by bending the knees or extending your legs. In this way you can move your centre of ballast to match back up with your centre of buoyancy. And, in doing so, manage to maintain a nice, 0° trim.

Think of a fulcrum. A see-saw. As tanks get breathed down their butts get floatier and floatier; this moves the centre of buoyancy lower and lower down your back. In essence, it makes one side of the see-saw lighter. Well… you’re not going to start stuffing rocks into your hood to add weight to the other side. (Wouldn’t work in cave diving anyway. Limestone is really light.) But, what you can do is move the pivot point. Make the light side of the see-saw longer. That length makes that side heavier again. Now… on to the weight placement and the why of it all. Take a glance up at the illustration of all those various forces of buoyancy and ballast acting on a diver. Where are the majority of buoyant forces vs. the majority of ballast forces? Notice that the wing (the biggest buoyant variable) is centred between the heavy side of the tanks and the “weight belt” (the biggest ballast variables). Now imagine if the “weight belt” arrow were placed even further up on the body. Such as, if a diver had placed v-weights near the top of the tanks to remedy perceived head-heaviness. Or if there were no weights at all. Or during an exhale and the lungs aren't a buoyant force anymore. All the sudden that whole drawing looks very suddenly like that diver would have a hard time keeping their head up, doesn’t it? Which is exactly what happens to so very many divers.

Those two arrows desperately want to meet up and create a little red pivot dot as in the illustrations above of balanced divers. With the centre of ballast at a point just behind the diver’s neck, and the centre of buoyancy somewhere around the middle of the diver’s hips or so, this is a system seeking equilibrium.

Unfortunately for our diver with the unbalanced weighting here, that means they would need to not only do a somersault into a head-down position, but the tanks would also very much like to be below them. So for equilibrium to be reached and the two arrows to

create their dot, our poor diver would wind up like this:

You wanna swim around like that? Yeah. Me neither. It’s an uncomfortable as hell feeling, that beginning of a somersault. Something in our early primate brain doesn’t like the idea of being upsidedown. So divers don’t let it happen. Even when I tell people, “Hold absolutely, perfectly still. Don’t try and correct anything as it happens to you, just go completely flat in the water and then stop all movement. No fin twitches. No hand movement. Not so much as a tightened muscle. Stay in that position and let whatever your body is going to do just happen.” I doubt most people even notice it. The way they twitch their fins or the way they arch their back. Or, most commonly, the way they throw their hips down.

With their body position altered like that they subtly move the two conflicting forces closer together. What’s more, it forces all the gas that should be cuddling their tanks from either side, like a little cloud for the weight to float on, up to their shoulders as the gas seeks the highest point. This moves the centre of buoyancy even closer up to their head-heaviness. Sure, it’s a bit more comfortable, but it’s not all the way to Stability Junction. The two arrows still want to meet, so if our diver stops moving completely now they’re likely to be pulled into vertical. To avoid this little corrections need to continue to be made… generally by way of moving the feet. Fucking constantly. Which introduces another three-fold problem.

  • When you move your feet with fins on, you move forward.

  • When you are trying to hold a precise position, but keep moving forward, suddenly you have to back-kick, but back-kicking effectively from that position is near impossible. And if you try to get into horizontal to do so you’re back to feeling like you’re going to somersault.

  • Constantly moving your feet in a place where it’s silty is… unwise.

When all you really needed to do was move some weights a little lower on the body. We have the technology. And alllllllllllll of that is bouncing around in the back of my head each and every time I have a student insist, “I definitely need more weight, but I need to move it much higher. Because I just can’t keep my feet up.” There are a lot of damn good instructors in the world. And they all want you to look like this:

So that you can hold perfectly still in the water. Which increases your comfort and control. Which frees up your mental capacity to pay attention to something other than, "HOLDSTILLHOLDSTILLHOLDSTILLOHFUCKOHFUCKHOLDSTILLHOLDSTILL!" This, in turn, increases your safety, your ability to be a good teammate, and your capacity to enjoy every dive as much as possible. To that end I’d suggest listening to whomever your instructor may be when they say, “I swear to Aquaman himself, you actually need to wear your weight lower.”

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