Sunday, 8 April 2007

Part 6: A discussion on diving and air consumption: Weighting

Correct weighting is essential for efficient air consumption.

Weighting is a key component in buoyancy control (discussed below) but also has a tremendous impact on your efficiency in the water. Overweighting tends to drag the lower part of the body down so even if neutrally buoyant, divers need to kick continuously to remain horizontal in the water. All that kicking requires energy which requires air. To make matters worse, if you are over weighted, you will need to add more air to your jacket to remain neutrally buoyant at depth – your jacket will therefore have more volume causing more drag through the water. A double whammy on your air consumption!

Additionally, the more weight you carry, the more inertia you have (think about a truck braking as opposed to a car) meaning it takes more effort to change direction and as we know effort equals air – is there such a thing as a triple whammy? Under weighting will have similar impact on your air consumption as you struggle to kick down towards the end of a dive whilst your tank is trying to pull you up.

Remember you will breathe 1.5kg plus of air during your dive so always adjust your weight for the air you expect to have at the end. If you are correctly weighted for 1 dive are you necessarily correctly weighted for another (assuming no changes in wetsuit etc)? Not necessarily! If diving in current, which is frequently in Fiji, I find it easier to be slightly over weighted. You can use less energy if having to swim into a current by ‘falling’ into it using your extra weight.

Also if there are up currents you can use the weight to your advantage without having to swim down.

At any rate, think about the dive you are doing and weight accordingly.