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trim and buoyancy in diving

We might become close to weightless underwater, but this does not mean that gravity cannot affect you below the surface. As you learn to dive, you will feel how the gravity together with buoyancy plays tricks on you.  

Let’s look at how this is affecting you in the water and how to use techniques and equipment to help you reach perfect trim.


Having the proper amount of weights reduces drag, makes it easier to fine tune buoyancy leading to greater comfort and less gas use. Here is how you should think

First find out the right amount by doing a weight check. A normal test would be to float at eye level at the surface with a near empty cylinder with an empty BCD, holding a normal breath. (not for technical divers who need to stay comfortable neutral at the last decompression stop)

Second, because the upper body has greater buoyancy (air in the lungs) than your legs, reduce the amount of weights on or below your waist.



Virtually all dive equipment has an impact on your trim as none is really neutral. Masks, snorkels and other accessories does not really matter, but wetsuits, fins and BCDs does affect you a lot. Here is how you should think

Using heavy fins with a shorty or board shorts in a tropical environment will pull your feet down. Using light or neutral fins in this case can make a big difference. However, heavy fins can be essential equipment for diving with a dry suit where air can potentially accumulate in the legs and feet (there are technique’s and equipment to keep this at a minimal also).

Using a standard jacket style BCD with a weight belt at your waist, can pull the upper body upwards. By having correct amount of weights you will need less air in the BCD and this will help with your trim. Another trick is to put a weight (for trim purposes only) on the cylinder band or in dedicated trim pockets.

A harness/backplate/wing style BCD has weights and bladder on the back also reduces this effect and forces the body to rest in a more stable position.

In recent years, Sidemount diving has gained popularity in recreational diving, and it’s a system focusing immensely on how equipment and its adjustability can create the perfect trim.

Read more here!



How you breathe and how you focus your balance will also affect trim. Here is how you should think

Taking unnecessary large breaths combines with shallow breathing will just like a BCD, increase buoyancy on the upper part of your body. With regular breaths, and exhaling properly will not only relax and oxygenate the body, but also keep the buoyancy to a minimum.

Keeping arms by the side and legs stretched out will make you unbalanced plus once again push weight further down and the trim can be affected. Balancing your body by shifting legs upwards and extending the elbows slightly in front of your shoulders helps to distribute weight forward on your body.

Of course because people vary in their physiology it will take some time to get the trim correct. Combining the above points and some imagination, you will reach the equilibrium and your perspective will open up underwater!


Fon Divemaster at Kon-Tiki Krabi

2017 COE Logos white bkg translations en US UK

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