There are 3 elements to diving with ease and grace: having the correct weighting, perfecting your buoyancy and mastering your trim. If you manage to get these 3 key aspects correct, you’ll be diving efficiently, safely and effortlessly in no time.
What Is Trim?
Trim is best explained as the angle at which a diver’s body is in relation to their direction of travel. For example, when your body is completely horizontal and running parallel to the surface of the water and the sea floor, your trim is neutral. When your body is slanted upwards slightly (so that your head is higher than your feet) it’s said that you are in positive trim, and conversely, when your body is at a downward slant with your head below your feet your body is in negative trim.
When Do You Use Trim?
In short, all the time! If you’re swimming up over an obstacle or ascending towards the surface, you’ll need to stay in positive trim. If you’re heading deeper into the water, you’ll need to stay in negative trim. When you’re keeping at the same depth, you’ll stay in neutral trim. This is where you should spend most of your dive, but all too often divers unwillingly vary their depth over the course of the dive as they fail to keep their trim in neutral. Maintaining neutral buoyancy is also cause for large depth fluctuations which can have serious implications.
Consequences of Using Incorrect Trim
When a diver’s trim is slightly positive, just one kick of their fins will drive them upwards, forcing them to constantly adjust in order to maintain a consistent depth. Avoiding diving in positive trim is especially important when muck diving, or if the sea floor has a silty consistency. Just one kick of your fins will kick up enough sediment to massively decrease visibility for your fellow divers, not to mention scare the tiny critters away which might be hiding in the silt. Failing to notice whether you are in positive trim or not can also have serious consequences when diving in an enclosed cave or tunnel where it is imperative to remain at the same depth throughout.
How To Achieve Neutral Trim
First things first: ensure you have a handle on your buoyancy and that you have the correct amount of weights. The vast majority of divers who find themselves incorrectly in positive trim are probably negatively buoyant, meaning that they’re carrying too much weight or haven’t adjusted their buoyancy correctly. This is the reason for their slightly slanted swimming style – they unknowingly compensate for their incorrect trim by using momentum (kicking their fins) which ultimately leads to an inefficient use of air and unnecessary loss of energy. Positively buoyant divers (those who are underweighted, carrying too much air in their BCDs or wearing a dry suit without correctly compensating for this in terms of buoyancy) will end up swimming at a downward angle to maintain a consistent depth. This again wastes precious time, energy and air.
Once you’ve managed to master your buoyancy and are carrying the correct amount of weight, keeping your body in neutral trim should be a piece of cake. It’s a good idea to test your trim skills by trying to hover in mid-water without slanting your body forwards or backwards or even onto your side. If you’re unable to do this, you might need to make some adjustments to your weight system. If you find yourself rolling forward, your weights should be moved further down and as far away from your torso area as possible. Consider using a weight belt rather than integrated weights in your BCD or making use of ankle weights. Another option is to shift your air tank further down. Similar tactics but in the opposite way apply if you slant backwards when trying to maintain neutral trim. For those who roll onto their sides when trying to maintain a neutral trim, it’s important to check that your tank is right in the centre of your back and that all your weights are distributed evenly. As a last resort, move some of your weights to the opposite side that you tend to roll onto and see if that compensates just the right amount to keep you in neutral trim.
Mastering your trim is most certainly a skill that requires a great deal of practice. Some aspects of your trim can be adjusted with how you have your weights set up and how you maintain your buoyancy, but in the end trim skills come down to the age-old saying, practice makes perfect. Remember that being as symmetrical as possible when under the water goes a long way to maintaining neutral trim.
As with buoyancy practice, your 3 minute safety stop is the ideal time to train and perfect your trim. Try hovering at the required depth in a completely neutral trim, that is, horizontal and parallel to the sea floor and the water’s surface. You’ll be working on both your trim and your buoyancy and by doing this at every safety stop you’ll find yourself quickly progressing towards effortless diver status.