In the discipline known as variable weight the freediver descends feet first on a weighted sled which runs along a rope. In the past freedivers would descend head first, but modern day freedivers choose to descend feet first because this makes the process of equalisation easier. On reaching the target depth the freediver must return to the surface by finning and/or pulling along the line. Freedivers usually wear thick neoprene suits (7-9mm) to give extra buoyancy which makes the ascent easier. This discipline requires excellent equalisation and breath-holding ability.
In short: going down on a sled and pulling back up a rope