The diver may use the sled for the descent and, in addition, an auxiliary device such as a balloon or lift-bag may be used to speed up the ascent as well. This is the deepest and most extreme of all freediving categories, and thus the most spectacular AND dangerous. The logistical and financial requirements associated with this category make it almost prohibitive, while setting up an effective safety system to protect the diver in case of an accident is also a very complex matter, a fact proven by the death of a diver during a record attempt in 2003.

Interesting Facts:

• This is the category upon which the popular film "The Big Blue" is based. It is in this category that women have equaled or surpassed men's records more often.
• The limiting factor for this category seems to be the great risk associated with it rather than the freedivers capacity, as in theory, humans could dive as deep as 500 meters/1450 feet!