What sort of weight belt is best for freediving?
There are two choices for the material of the weight belt, webbing and rubber. Rubber is the superior choice because of how snug it fits even as the body and wetsuit gets compressed and reduces in size. A webbing belt is quite adequate for shallow recreational diving, but as the diver gets deeper a rubber belt has the property of reducing its size with the change of size of the freediver under pressure.
There are two choices of weight belt buckles, what one is best?
When using a webbing belt the Quick Release buckle is best and universally recommended. However, rubber weight belts tend to be thicker and when using a Quick Release buckle the belt often doesn’t drop away immediately when released and the belt may need to be assisted through the buckle.
The Marseillaise buckle works better for the thicker rubber belts. This is the buckle that looks like the standard belt buckle with the rod going through holes in the belt material. When the belt is released, the buckle is designed so the rod springs out allowing a larger area for the belt to slip through. There is also a roller on the buckle edge to encourage the rubber belt to slip through.
Why do freedivers use neck weights?
Neck weights are used mainly in the swimming pool for training and competition pool disciplines. Their purpose is to get the correct ballast to allow a diver to achieve a horizontal position while swimming. Lungs full of air create a huge uplift. If they are not balanced with the correct amount of weight it causes the freediver to waste energy trying to constantly keep below the surface and they move through the water like a plough rather than an arrow. The best place to carry weight to balance the floating effect from the air in the lungs is around the neck, hence the neck weight. Many freedivers also wear some weight around the waist, especially when wearing a full length wetsuit to counterbalance the upthrust of the wetsuit neoprene on the legs. The ideal weight and arrangement will allow a freediver to push off from the wall at the optimum depth in the pool, and with no further propulsion, continue travelling on the same plane without sinking or floating.