What is Trim?

Have you been on a dive and felt you had to swim really hard to keep up? How about your feet seem to always be headed for the surface? Maybe you keep hitting the bottom or your buddy with your fins? These are problems associated with your trim. We'll take a look at trim and go over ways to improve it.

Trim is how our body is positioned in the water 3 dimensionally, the better our trim, the less resistance we produce while diving. The goal is to have as little surface area making contact with the water in the direction you are traveling as possible. This means your body should be flat, parallel like a skydiver or a missile and your arms close to your body and parallel as well. Think of a piece of paper. Try to throw a flat sheet and it goes no where, but ball it up and you can throw it across the room. Less resistance, easy travel.

The way we kick and hold our arms directly relates to trim. Kicking from our knees instead of our hips can cause us to bicycle kick which drops our legs below our torso. Having our arms out to our sides may cause our trim to roll us to one side and it creates drag. Kicking rapidly or excessive body moment can throw off our trim as well. Body types affect trim too especially with women. Using heavy fins, how about a full face mask? Equipment has a large impact as well.

Sinking feet

Sinking feet is common with most new divers and directly related to kicking and weight. A diver may be over weighted and to compensate they kick downward, a simple weight check at the beginning and end of the dive can fix that. As stated above, kicking from the knees can cause this. I often video students in the pool that do the Peak Performance Buoyancy class so they can see how they kick. Kicking from the hips is important not just for trim but for swim efficiency, it also protects the coral and your buddy.

If you're kicking from the hip and you still find your legs sinking, there are a few other things you can try:

  • Weight check. If you have a lot of air in your BCD to stay neutral buoyant it affects your trim.
  • Shift your tank up a little. A little nudge may be all you need to fix the problem.
  • Arm position. Try holing your arms out in front of you in a relaxed position, hand over hand. This acts as a counter balance.
  • Equipment. Are your fins tanks? My warm water fins weight 3 pounds while my cold water fins weight 11. Those 11 pounders will throw off my trim in warm water due to less gear
  • Trim pockets. Try putting a few pounds in trim pockets or on the cam band of your tank. Don't put all your weight there because you need to be able to ditch some at the surface in an emergency.
  • 5mm boots. 5mm neoprene will make your feet more buoyant.
  • Diving full face mask? That can add 2 pounds or more of positive buoyancy to your upper body. Compensate with a shoulder weight.

Floaty Feet

Floaty feet is not as common as sinking feet but it happens. I have seen this with bodybuilders who have well developed torsos (don't skip leg day). Dry suit divers experience this issue when the air from the suit goes to their feet.

Things you can try:

  • Moving weights from your trim pockets, if you have weight in them, to your waist.
  • Try shifting your tank down.
  • Keep your arms at your sides, many hold the bottom of the tank as a reminder
  • Fins. Those 3 pound travel fins may be great, but a 5 pound pair could solve the issue
  • Boots. Wearing 5mm in warm water, try 2 or 3mm.
  • Ankle weights. I'm not a fan but many swear by them.
  • Dry suit divers try using gators. They slow the travel of air to your feet. Of course a well fitted dry suits helps too.

 

Dangalies

Loose hanging items are not only bad for environment, they cause a lot of drag and the swaying motion of those items affect your body position in the water. A console with a spg, depth gauge and compass is pretty heavy. Unsecured it could cause you to lean to one side. Shifting your body to compensate causes unnecessary movement further affecting your trim. If there is surge the issue is compounded.

Keep items secured close to your body. Store something like a heavy console closer to the center of your body, perhaps tucked in your waist strap. Octos should always be secured in the "triangle". Diving with a camera affects your trim, especially if its in a medium to large size waterproof housing or you are using a Go Pro floaty handle. Placement of things like knives, lights smbs and reels should be taken into account too. They should be distributed evenly, not all on 1 side
There are many aspects to trim, more than I can cover in this article but I hope now you have a basic understanding of what it is and some common issues. Taking a course like Padi Peak Performance Buoyancy will give you the advantage of working with an instructor and fine tuning your trim and buoyancy to perfection. You can also work on these things on your own as well, if you have access to a pool thats a big plus.
Tags
peak
buoyancy
weight
trim
kick

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