Last updated: 3 October 2026
Reviewed by Jordan Morley, FA Level 2 Football Coach
Open water swimming takes place in natural bodies of water rather than pools. It introduces challenges absent from pool swimming: navigation (sighting), currents, waves, cold water and variable visibility. Triathlon swim legs are almost always open water. FINA/World Aquatics sanctions marathon open water events at 10km (Olympic) and 25km (world championship). Most open water swimmers add 8-15% to their pool pace to estimate open water times. Safety practices include never swimming alone, using a tow float and knowing conditions.
- Natural water: lakes, rivers, oceans
- Navigation (sighting) is a key skill
- 8-15% slower than pool pace for most swimmers
- Always swim with a partner or group; use a tow float
In practice
Open-water swimming introduces challenges a pool never does — navigating without lane lines (sighting the course periodically), coping with waves, currents and cold water, and swimming in a tightly packed group (drafting off other swimmers to save energy, much like cycling) — which is why most triathletes and open-water racers train specifically in open water before a race rather than relying purely on pool fitness.
FAQ
What is 'sighting' in open-water swimming?
Periodically lifting the head slightly to look forward and check direction against course markers, since open water lacks the lane lines a pool swimmer normally uses to stay straight.
Does drafting work in open-water swimming like it does in cycling?
Yes — swimming closely behind or beside another swimmer reduces drag and can meaningfully save energy, a tactic frequently used in competitive open-water and triathlon swimming.