Freediving Disciplines Explained - CWT, FIM, STA, DYN and More

The alphabet soup of freediving disciplines can be confusing when you first join a training group. People talk about their CWT personal best, a new DYNB distance or a slow STA session, and it sounds like a different language. Each abbreviation simply describes how a dive is done - where it happens, which direction you go and what equipment you are allowed to use.

This guide explains every major discipline, what each one trains, which ones beginners should start with and how competitions work in general terms. Federations update their rules over time, so if you plan to compete, always check the current rulebook of the organization running the event.

The two big families - depth and pool

Freediving disciplines fall into two main groups:

• Depth disciplines take place in open water along a vertical line. You dive down to a target depth, collect a tag or turn, and come back up.
• Pool disciplines take place in a swimming pool. You either hold your breath without moving (static) or swim horizontally underwater for distance (dynamic).

There is also a third group of extreme, record-only categories that use machines or sleds to move the diver. These are covered briefly below, mainly so you know what the terms mean.

All the disciplines at a glance

The depth disciplines

Constant weight (CWT)

CWT is the signature discipline of modern freediving. You descend and ascend using fins and body power alone, and you cannot pull on the line except to stop or turn at the bottom in some rule sets. You must also come back with the same weight you started with, which is where the name comes from.

Monofins are common in competitive CWT because they are very efficient, but they take time to master. CWT teaches you to fin efficiently on the way down, then relax completely in freefall once you become negatively buoyant. It also places big demands on equalization, because you are moving quickly and must equalize hands-free.

Constant weight bi-fins (CWTB)

CWTB is constant weight done with two separate fins rather than a monofin. Federations added it as its own category because so many recreational divers use bi-fins. If you train with long carbon or plastic freediving fins, this is likely the discipline you are already doing.

Constant weight no fins (CNF)

CNF is constant weight with no fins at all. You use a breaststroke-style arm pull and kick, gliding between strokes. It is slow, beautiful and technically demanding. Many experienced freedivers consider it the purest discipline because there is no equipment to hide inefficiency, and the depths reached are noticeably shallower than with fins.

Free immersion (FIM)

In FIM you pull yourself down and up the line using your arms, with no fins. Because you control your speed with every pull, it is a wonderful discipline for learning to equalize, staying relaxed and exploring depth gradually. Many instructors use FIM early in courses and coaches use it for warm-up dives and equalization work.

Variable weight (VWT) and no limits (NLT)

These are extreme categories in which the diver rides a weighted sled down the line. In VWT the diver returns under their own power, often by pulling or finning; in NLT a lift device such as an inflatable bag brings them up. They are not part of standard competitions and are done only as individual record attempts with large professional safety teams, medical support and specialized equipment.

They are not recreational disciplines. The depths and speeds involved create serious risks that ordinary buddy safety cannot manage, so treat them as something to read about, not to try.

The pool disciplines

Static apnea (STA)

Static is holding your breath while floating face down in the water, completely still. It sounds simple, but it is a deep exercise in relaxation and mental control. Static teaches you to recognize the urge to breathe, to stay calm through contractions and to keep your heart rate low. It is also where many people first discover how much longer they can hold their breath than they imagined.

Static must always be done with a trained buddy beside you, touching or watching closely and running a simple signal protocol. Our guide on how to hold your breath longer covers how to train for it safely on land.

Dynamic with fins (DYN) and dynamic bi-fins (DYNB)

Dynamic is swimming horizontally underwater along the pool for distance. DYN is typically done with a monofin, and DYNB is the separate category for bi-fins. Rules differ slightly between federations, so check which fins count for which category.

Dynamic trains efficient finning, streamlining, neutral buoyancy at shallow depth and the ability to stay calm while working. It is excellent preparation for depth because many of the same skills transfer directly to CWT.

Dynamic no fins (DNF)

DNF is the pool version of CNF: a breaststroke-style underwater swim, with a long glide between strokes. It is slow and elegant, and it teaches timing and body position better than almost anything else. Because the body is working with large muscles, it also teaches you to manage oxygen consumption carefully.

Which discipline should you start with?

For most new freedivers, the best path is to learn on a course and build a foundation in four disciplines:

1. Static (STA) in the pool to learn relaxation and how your body responds to breath-hold.
2. Dynamic (DYN or DYNB) to build finning technique and comfort underwater.
3. Free immersion (FIM) to learn equalization and depth at your own pace.
4. Constant weight bi-fins (CWTB) once your duck dive, finning and equalization are reliable.

CNF and DNF are worth adding once you have solid basics, because they will improve your technique in every other discipline. Monofin work usually comes later still, often after an intermediate course.

What each discipline trains in your overall freediving

Different disciplines develop different qualities, and most divers improve fastest when they mix them:

• Relaxation and mental control - static and free immersion
• Equalization - free immersion and slow constant weight dives
• Efficiency and technique - dynamic and no-fins disciplines
• CO2 tolerance - dynamic and static training, plus dry tables on land
• Depth adaptation - gradual, well-supported constant weight and free immersion

Competition basics

Competitions are run by federations such as AIDA and CMAS, and each has its own rulebook. The core ideas are similar:

• Announced performance. Before the event, each athlete announces the depth, distance or time they plan to achieve. For depth disciplines, the bottom plate is set to that depth.
• Official top. Each athlete has a scheduled start time and must begin the dive within a set window.
• Surface protocol. After surfacing, the athlete must complete a specific sequence within a short time - typically removing face equipment, giving an OK sign and saying a set phrase - to show they are fully conscious and in control.
• Cards. Judges usually show a white card for a clean performance, and other colors for penalties or disqualification, such as missing the surface protocol, pulling on the line in CWT or showing signs of a loss of motor control.
• Safety team. Competitions use dedicated safety freedivers and medical staff. A buddy is not enough for competition-level dives.

If competition interests you, start by volunteering or watching a local event. It is a great way to understand the rules, the safety system and the culture before you ever announce a dive yourself.

Training any discipline safely

Whatever discipline you love, the safety basics never change. Train with a qualified buddy, follow the one-up one-down rule, build depth and distance gradually and always perform a calm breathe-up and proper recovery breathing. Our article on freediving safety rules and the buddy system goes into detail.

Most divers have a favorite discipline, but the strongest freedivers train several. When you are looking for people to train with, it helps to find buddies who share your discipline and level - that is one of the things BuoyBuddy, our upcoming freediving buddy-finder app for iOS and Android, is designed to make easier.

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