Deep-Sea Sherpa

Before we put the basic levers for trim in use, it’s very important to review the horizontal trim position. For the majority of scuba divers, the horizontal trim position is not natural.

Horizontal Position

Consider the body in the horizontal plane. Now consider where the head needs to be for the body to be in the horizontal position. Yes, the head needs to be back against the 1st stage or tank manifold.

In addition, the legs (or more appropriately the knees) need to be up. This requires the flexing of the glutes and consideration of not “dropping the knees.”

Lastly, your back will be in a slight arched position (as shown in the diagram below.) A fellow diver, Lynne, makes a good recommendation regarding this position: “With regards to the part about body positioning, I always have a little bit of an issue with telling people that they should arch their backs. Too often, they try to make the whole movement with the small of their back, which results in significant back pain. I tell people to make their body as long as it can possibly be from the shoulders to the knees, and then contract the glutes to flatten out the hip joint. That seems to avoid the hyperlordosis issue.”

Getting familiar with the horizontal position on dry land is the first step. Using either a bench, a bed, or the floor, assume the prone position and look straight ahead. Do not cheat, and lift the knees off the ground. Remember what muscles are used, since these will be the ones needed in the water as well.

While on dry land, having an instructor or a knowledgeable buddy review your position will be beneficial. In lieu of a buddy, a mirror can be used.

Below are scuba divers in an Essentials class getting into horizontal trim.

Once in the water, it is initially difficult to tell if one is in horizontal trim. As the result, video taped class sessions are often eye opening for many divers. Besides video, a good buddy can simply signal the degree of attack that he is seeing. Some instructors employ mirrors in pools to aid the diver as well.

If possible, free dive a swimming pool or the ocean. Drop down and hover in horizontal position (a few pounds on a weight belt will be sufficient). Without the extra buoyancy of wetsuits and additional weight of gear, getting into the correct positioning will be easier. Once this position becomes familiar, then don all the scuba gear.

Proper Weighting

Proper weighting cannot be stressed enough to new (and some experienced) divers. Overweighting is the root of many problems in scuba, and trim is definitely one of them.

The more weight that a diver carries beyond keeping him neutral, the more air must be carried. More air equals larger bubble. Larger bubble equals more management and exaggerated vertical movement. For example, you rise a little, the bubble expands generating more lift causing you to rise more. As the result, it’s best to minimize the amount of air carried.

Appropriate BC Lift

Another common mistake is selecting a BC with too much lift. The actual issue isn’t the lift, but it’s the excess material of the BC that’s needed for generating the lift. In order to provide more lift, the larger BCs need to be wider and or longer.

While more material generates more drag, it impacts trim as well. The extra material ultimately requires more active management from the diver and in some cases lead to trapped air.

Use of Levers

Once the diver knows and feels what horizontal trim feels like, then we can begin using buoyancy, weight and leverage to aid him.

Step 1: Find a comfortable spot and drop to 20′ of water. Get into horizontal position and do not move. Do not move the hands, do not move the fins. If need be, cross the hands and fin tips so there is no subconscious movement. The body should simply be pressing in the horizontal position.

Step 2: Count to 5. 1-2-3-4-5. Is there instability in pitch? Are the feet lifting you to the surface? Are the feet sinking even though you are flexing to keep the knees up? Is the head being driven into the ground? Is the torso being lifted up?

Step 3: Repeat 1 and 2, adjusting arm and leg position as levers to correct trim issues. For scuba divers in warm water (minimal weight and exposure protection), body positioning is often sufficient to correct trim issues.

Step 4: If these adjustments do not resolve the issue, then check buoyancy and weight locations. These will need to be adjusted.

For example, let’s assume that a properly weighted diver is in head heavy doubles rig. What are the options?

1. Move tanks down
2. Move wing up
3. Get longer tanks
4. Get a tail weight
5. Move to an aluminum plate and use a heavier tail weight
6. Weight belt
7. Get heavier fins
8. Ankle weights (*gasp*)
9. If diving dry, dive with air in your arms
10. If diving dry, add a vest
11. If diving dry, use fin keepers and/or gaiters (maybe it’s floaty feet)
12. Use a wing with lift at the shoulders

There are pros and cons with each of these approaches.

For in water training, I recommend UTD Essentials or GUE Fundamentals. Both courses have proven track records of cultivating the basic diving skills.

Related Posts

• Scuba 101 – Controlled ascents
• Scuba 101 – Ascents and Descents
• Horizontal Trim 101 – Levers

Filed under:
How To, Training by Don