Freediving has its own alphabet — STA, DYN, DNF, CWT, CWTB, CNF, FIM, VWT, NLT. If you're new to the sport, this looks like gibberish. But each abbreviation represents a specific discipline with its own rules, techniques, and training applications. Here's what they all mean and which ones matter for your training.
Pool disciplines
These are performed in a pool and focus on breath-hold duration or horizontal distance. They're the foundation of freediving training because they isolate specific skills without the complexity of depth, equalization, or ocean conditions.
STA — Static Apnea
Holding your breath without movement, usually floating face-down at the surface. STA measures pure breath-hold time. It's the most mental discipline in freediving — your body is still, so it's entirely about relaxation, CO₂ tolerance, and the ability to stay calm as the urge to breathe builds.
AIDA requirements: 2:00 min (AIDA 2) · 2:45 min (AIDA 3)
Training value: STA is where you learn the fundamentals of the mammalian dive reflex, diaphragm contraction management, and mental composure. Every other discipline builds on the capacity you develop here.
DYN — Dynamic Apnea with Fins
Swimming horizontally underwater with bi-fins or a monofin. DYN measures distance covered on a single breath. It combines breath-hold capacity with efficient movement — you need good technique (streamlining, kick cycle, glide phase) to minimize oxygen consumption.
AIDA requirements (DYNB — bi-fins): 40m (AIDA 2) · 55m (AIDA 3)
DNF — Dynamic Apnea without Fins
Swimming horizontally underwater using only a modified breaststroke — no fins. DNF measures distance and is the most physically demanding pool discipline. It requires excellent body control, streamlining, and energy efficiency since you're generating all propulsion with your arms and legs.
DNF isn't part of AIDA recreational certification requirements, but it's a powerful training tool. If you can swim 50m DNF, your finning efficiency will be dramatically better because you've learned to minimize drag.
Depth disciplines
These are performed in open water using a vertical dive line and measure maximum depth achieved. This is where freediving becomes a three-dimensional sport — you're adding equalization, pressure changes, buoyancy shifts, and the psychological dimension of depth.
CWT / CWTB — Constant Weight (with fins / with bi-fins)
Diving vertically with fins, descending and ascending under your own power. You cannot pull on the rope or drop weights — what you take down, you bring back up. CWT is the flagship depth discipline and what most people picture when they think of freediving.
CWTB (the "B" means bi-fins specifically, as opposed to a monofin) is the standard in AIDA training courses.
AIDA requirements (CWTB): 12–20m (AIDA 2) · 24m (AIDA 3)
What makes it challenging: As you descend, buoyancy shifts from positive to negative around 10m. Above that, you're fighting to get down. Below it, you're sinking and need to control your descent speed. Equalization gets progressively harder as your lung volume compresses — from 6L at the surface to 3L at 10m to 2L at 20m.
FIM — Free Immersion
Diving by pulling yourself down and up the rope — no fins. FIM is often the first depth discipline beginners learn because it eliminates the complexity of finning and lets you focus entirely on equalization and relaxation at depth. You control your speed precisely with your hands on the rope.
FIM is included in AIDA 2 and 3 training. Many experienced divers use FIM as a warm-up before CWT dives because it's gentler on the body and allows more focus on equalization practice.
CNF — Constant Weight without Fins
Diving vertically without fins, using only arm strokes and a dolphin kick. CNF is considered the purest depth discipline — no equipment assistance at all. It's the most physically demanding way to reach depth and requires exceptional efficiency and body awareness.
CNF isn't part of recreational AIDA courses, but it's a respected competitive discipline. If you see someone's CNF number, it tells you a lot about their overall freediving ability.
Specialized disciplines
VWT — Variable Weight
Descending with a weighted sled and ascending by finning or pulling the rope. VWT allows you to reach depths beyond what your equalization or fitness would normally permit on the descent, while still requiring you to ascend under your own power. It's a training tool more than a competitive discipline in most contexts.
NLT — No Limits
Descending with a weighted sled and ascending with a lift bag or other assistive device. NLT is the discipline that produces the deepest numbers — over 200m in some cases — but it's not part of AIDA recreational education. It's a specialized, high-risk discipline reserved for experienced athletes with extensive safety infrastructure.
Which disciplines will I learn?
In AIDA certification courses, you'll train these disciplines:
- AIDA 1: STA introduction, basic finning
- AIDA 2: STA, DYNB (dynamic with bi-fins), CWTB (constant weight with bi-fins), FIM (free immersion)
- AIDA 3: All AIDA 2 disciplines at higher standards, plus CO₂/O₂ table training and advanced equalization for depth
In our weekly group sessions, we practice a mix of all disciplines depending on whether we're in the pool or the ocean. CWT and FIM get the most ocean time. STA and DYN are the focus of pool sessions and dry training.
The bottom line
You don't need to memorize all these abbreviations before your first course — your instructor will teach each discipline as it comes up. But understanding the landscape helps you see where freediving can take you. Most people start with STA and CWTB in their AIDA 2 course and discover that each discipline develops a different aspect of their diving. STA builds mental composure. DYN builds efficiency. CWT builds depth confidence. FIM builds equalization skill. Together, they make a complete freediver.
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