Dynamic apnea with fins (DYN) is an AIDA International (International Association for Development of Apnea) freediving discipline in which the freediver travels in a horizontal position under water under the diver’s own power without the aid of a physical surface except the pool wall when competing indoors. Any propulsion aids other than fins or a monofin and swimming movements with the arms are prohibited. Records are recognized only in pools of 25m or greater.
When diving in the dynamic without fins category, divers will usually prefer the shorter 25m pools, so they can take advantage of the wall-kick. On the contrary, when diving in the dynamic with fins category, divers will usually prefer the longer 50m pools, so the wall-turn will not slow them down.