Free-diver descending with the aid of a rope. Free-diving is an extreme sport where the diver wears only a mask, flippers and swimwear. They do not rely on air tanks, instead they take a large breath of air at the surface before descending. This free-diver is using a clip to stop water going up his nose. Well trained free-divers, or apneists, can hold their breath for up to 7 minutes.