AIDA (Association Internationale pour le développement de l’Apnée – Worldwide Federation for breath-hold) recognizes only 8 categories of freediving which are:
Constant Weight Without Fins (CNF):
It is the most difficult discipline because there’s no help, you have no equipment. It consists to descend and ascend under water by using only your own muscle strength, with no equipment, no propulsion, no pulling, etc. For this category, you have to get a perfect coordination with your body because muscles consume a lot of oxygen so you have to control your movements with your buoyancy, and your oxygen.
Constant Weight (CWT):
With this category you must descend and ascend with your fins or your monofin and you can help you by using your arms but without pulling on a rope. This category is the most common in freedinving thanks to fins you can use.
Dynamic Without Fins (DNF):
You have to cover the greatest distance in a horizontal position. Any propulsion aids are prohibited. You don’t need any propulsing material but you have to get a good technique to cover the better distance. This category is practiced in pool only and performances are recognized for distance cover over 25 meters.
Dynamic with fins (DYN):
It’s the same as the dynamic without fins category, but fins and monofins are allowed but not any other propulsion aids. It is also practice only in pool and performances are recognized only for distance over 25 meters.
Static Apnea (STA):
It is the only discipline which measures the duration. You have to hold your breath for as long as possible, your body can be in the water or at the surface. Performances are recognized in pool, but also in open water (sea, river, lake, etc.)
Free Immersion (FIM):
You dive under water by pulling on the rope during the descent and the ascent. It seems that it is the discipline with the purest sensations in freediving because of the speed of the water against your body, and the sensation of freedom. The performance could be valid the feet first during the descent or the head first.
Variable Weight (VWT):
In this category you descend with the help of a ballast weight and you ascent with your own muscle strength of your arms and legs either by pulling yourself or not on the rope.
No limit (NLT):
You descend with the help of a ballast weight and ascend with the method you want. You go down with a sled and you back up with a balloon, and you dive with a diving suit or a vest with inflatable compartments, or other means. The goal is to reach the deepest point you can and wait the minimum oxygen you can to back up quickly with the balloon.
If you want to try freediving and take courses, at SSS Phuket, we offer AIDA courses with theory and practice which lead to certifications.
Source: http://www.aida-international.org/aspportal1/code/page.asp?ObjectID=39&CountryID=4&actID=3