Perfect Trim for a Scuba Diver
If you are completely horizontal when swimming or hovering parallel to the surface or bottom, you’re in neutral trim. If you’re slanting upward, so your head is higher than your feet, you’re in positive trim; if you’re slanting downward, so your head is below your feet, you’re in negative trim.
The trim is the ideal horizontal position for a diver underwater, so we would like to share a couple of tips to achieve that perfect trim which will help you make the most of your dive and be a better diver as well.
The term “trim” comes from the English “cut” as in cutting the water to move, but it also means being or staying balanced. It is used as a nautical or aeronautical term to describe the balance of ships by adjusting the position of the cargo.
Having the correct trim is essential in diving and is a skill that should be required and mastered right after achieving neutral buoyancy.
Benefits of a good trim:
- Improve your air consumption:
When diving with a good trim, we are better prepare to go “against” the water in the direction in which we move and, therefore we displace a smaller amount of water, reducing both effort and the amount of air we use.
Also, the water thrust we create with our fin kicks gets aligned with the horizontal displacement we´re looking for, which makes us more effective, therefore less effort to move, leading to a better air consumption.
- Protect underwater life and yourself:
Few things bother me as much as seeing other divers with an incorrect trim, diving vertically, knocking corals, hedgehogs and other innocent creatures that are not to blame for the diver’s poor performance.
You should also try your best to stay horizontal and avoid touching sea life to prevent you from getting hurt with fire coral or other venomous creatures underwater.
- Maintains a good visibility:
When you don’t have the correct trim and fin kick near the bottom, the water you move “down” removes the bottom and sediment, creating a real sand/ dust cloud that can reduce visibility to zero. This is specially annoying when diving in places with silty bottoms, making it essential to maintain a horizontal position to avoid heavy fin kicks that will remove light substrate, ruining the visibility for everyone in the dive.
This is a normal behavior for OW divers that are just learning to perfect their technique, being an Instructor’s number one goal to reinforce the importance of neutral buoyancy and a proper trim.
- Facilitates breathing:
When horizontal, both our lungs and regulator are at the same “depth”, which means we have to make less effort to breathe. When in an upright position, the lungs are at a slightly greater depth than the regulator, so to expand during inhalation, they will be a little bit more forced under more pressure.
In deep dives, where it is important to keep the effort to a minimum, this can make a very big difference in our performance and the way we feel during the entire dive.
How to Achieve a Perfect Trim?
Achieving a perfect trim is a matter of balancing forces. Contrary to what it seems, this is a diving skill that is mastered with actions you must take into account outside the water, rather than in it.
Diving involves various forces, some positive (which make us float) and some negative ones (which make us sink). If the result of both is not aligned, the positive forces will create a momentum (turning force), with the exceeding negative forces making our body rotate until both forces are aligned, resulting in a semi vertical position, which is an incorrect trim.
BCD-induced buoyancy: (Buoyancy Control Device) This is located halfway through our vest.
Tank: In general our tank has negative buoyancy at the start of our dive, but at the end of the dive it turns positive, anyway, the force that is going to push us upwards, is in the middle of the tank.
Body: Our body, especially when we have a thick wetsuit (which is aggravated in cold water diving) will have positive buoyancy and this force is concentrated around our navel.
Main Weight position: The weight we carry either in a belt at the waist or in the BCD pockets, if we have integrated weights. This force’s influence is located in the area around the weights.
Weights for Trim: Well, these weights are usually on our back just below our shoulders, especially to keep us well trimmed and in a more horizontal position.
Of course there are other forces that affect trim, like the different types of equipment and dive accessories, but the main idea doesn’t change and they are not usually that important because they don’t have a major influence on our buoyancy or our diving position.
Anyway, we can always rearrange the weights in our BCD, and play with the distance between the weight blocks around the tank strap, in the same way the shape and distribution in which the weights are positioned, will have an impact on the way the forces balance to give us a good trim.
Every diver is different and will have to finds what formula works best for them. But if you keep these in mind and try to apply them, you’ll definitely find it easier to get a proper trim in no time!
About the author: Nora is a dive instructor at Deefer Diving. Originally from Patagonia, she fell in love with Carriacou when she first came here 3 years ago. It has now become a home for her.
For more information about diving in Carriacou, please visit our website,