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Achieving Ideal Trim

Published on: 2nd November, 2016 | Reviews and Training Tips
Photo credit: Ashton East on Canon S95 (compact)
Do you know what ideal trim looks like and why it is better for you and the reef? Do you know how to achieve it?

See also our Gear Guide for Buoyancy Control to learn more about achieving ideal trim.

You will hear trim mentioned a lot, but what is it? It is defined as diving in a horizontal position with your body parallel to the floor of the ocean/cave or shipwreck whilst presenting the minimum amount of physical resistance to the water in the direction you wish to travel. Imagine a torpedo in the water – positioned for low resistance and the efficient energy output. It is shown by the position of the diver in our logo.

Diving in a horizontal position allows the diver to direct the propulsive thrust from the fins directly to the rear, minimising disturbance of the bottom and the risk of striking delicate organisms with the fins. You avoid destroying the natural environment and the visibility. Good trim reduces the effort required to move around and maintain buoyancy leading to improved air consumption and reduced task loading.

There are two types of buoyancy control devices used for backmount scuba diving: jacket style BCDs (“BCD”) or backplate wing and harness (“BPW”)

The BCD is a single piece wearable sleeveless jacket integrating an air bladder, which wraps around the diver and naturally pulls the diver into a head up position. It is best suited for divers who need to maintain a vertical orientation underwater (for some reason) or spend a lot of time on the surface. The BCD remains the most popular choice for recreational divers all over the world.

The BPW is simple: a length of webbing threaded through a pressed metal plate and attached to a protected bladder. The BPW naturally pulls the diver into a horizontal position, allows for a lot of customization, and allows a natural progression from single tank to twin tanks and beyond without drastic changes in equipment.

For these and other reasons the BPW is by far the superior equipment choice. As avid and experienced divers ourselves we recommend BPW for all our divers, from their first open water course.

AUTHOR

Robert Main

TEC and CCR Instructor, JJ-CCR Diver

Ashton East

OC and CCR trimix, stage cave, underwater photographer; NSW, QLD and UK Legal Counsel.

Cameron Bull

TEC Instructor, JJ-CCR Diver, Cave Diver