The four strokes
Each stroke has strict rules about body position, arm recovery and how the wall must be touched. Freestyle is technically unrestricted, but everyone swims front crawl because it is the fastest.
- Freestyle — any stroke; in practice always front crawl
- Backstroke — on the back throughout, except during the turn
- Breaststroke — simultaneous, symmetrical arm and leg movements
- Butterfly — simultaneous arm recovery over the water with a dolphin kick
The pool
Long course racing uses a 50 m pool; short course uses 25 m, which produces faster times because there are twice as many turns and push-offs. Lanes are 2.5 m wide with floating dividers designed to absorb waves, and the water is deep enough that turbulence dissipates rather than bouncing back.
- Long course — 50 m, used at the Olympics and outdoor Worlds
- Short course — 25 m, with separate world records
- Lane ropes disrupt waves between swimmers
- Backstroke flags sit 5 m from each wall as a turn warning
Starts and turns
All races except backstroke begin with a dive from a starting block. A single false start means immediate disqualification — there are no second chances. Underwater, swimmers may travel a maximum of 15 m off each wall before their head must break the surface, a limit introduced because underwater dolphin kicking is faster than swimming.
- One false start disqualifies the swimmer
- Maximum 15 m underwater after each start and turn
- Backstroke starts in the water, holding the block
- Breaststroke and butterfly require a two-hand simultaneous touch
The events
Distances run from a 50 m sprint of around twenty seconds to the 1500 m, which takes about fifteen minutes. The individual medley requires all four strokes in a fixed order by one swimmer; the medley relay uses four swimmers in a different order, because backstroke must start in the water.
- Sprints — 50 m and 100 m
- Middle distance — 200 m and 400 m
- Distance — 800 m and 1500 m
- Individual medley — butterfly, backstroke, breaststroke, freestyle
Relays and exchanges
Four swimmers each cover an equal distance. The outgoing swimmer's feet must stay in contact with the block until the incoming swimmer touches the wall, and the margin is measured to the hundredth — an early takeoff of 0.01 s disqualifies the entire team. Well-timed exchanges are worth several tenths across a relay.
Suits and records
Full-body polyurethane suits in 2008 and 2009 produced a wave of records so extreme that World Aquatics banned them outright from 2010. Some of those records stood for over a decade afterwards, a permanent asterisk in the record books. Suits are now limited in material and coverage.
