Some dive gear is positively buoyant and the body generally tends to float rather than sink, which is why divers use weights to ascent into deeper waters on a dive. When choosing weights, there are several things to consider:
1) How much weight you will need. Your natural buoyancy will depend on your body fat, muscle amount, body type, and other factors. If you tend to float upwards in the water, you will need more weights. As well, the type of diving gear you use can affect your buoyancy. For example, if you wear a thick wetsuit, you will have more buoyancy than a diver with a dry suit diving in warm water. Even your gender can affect your buoyancy. Women tend to need more weights than men.
2) Types of weights. The traditional weight belt is still used, but more and more divers are using integrated weights worn in the BCD. A weight belt is secured around the waist but can put extra weight on the back and waist. Many divers prefer integrated weights, which are distributed over the BCD. Integrated weights can be added or removed gradually, allowing for controlled ascents and they do mean a more even distribution of weight. If you have back problems, you may appreciate the fact that integrated weights put less stress on your lower back.
3) Hard weights vs. soft weights. Hard weights are manufactured from lead. Some hard weights are coated with plastic for added comfort. These weights can easily be adjusted, simply by sliding the weights on and off the belt. Since the weights are made from lead and are rigid, however, many divers find them less comfortable than soft weights. Soft weights are usually made from lead shot contained in a soft mesh pocket. Soft weights can be either in the form of pouches or belts. Since these weights shift and assume a diver’s shape as the diver moves, soft weights tend to be more comfortable. They are also flexible because they can be worn on different parts on the body. Soft weight belts cannot be as easily adjusted as hard weight belts, although some manufacturers are changing that by allowing Velcro pouches on the belts so that the weights can be redistributed, even underwater.