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The sport of aquathlon consists of a continuous, two-stage race involving swimming followed by running. The International Triathlon Union (ITU) and its member federation organizations sanction competitions and govern the sport. An aquathlon is also called an "aquathon." The ITU and USA Triathlon sanctioning organizations generally use the term aquathlon.
Aquathlons have been around in various forms since the early 20th century in ocean lifeguard competitions. The National Surf Lifesaving Association of America, formed in 1965, held its first national competition that year and the events included a run-swim-run. The modern international standard lifeguard distance is 400 meter run - 400 meter swim - 200 meter run.
Aquathlon in general follows triathlon distances, but there is variability. Mostly open-water but there are some pool-based sprints/super-sprints.
ITU "Warm water" standard distances are 2.5 km run, 1000 m swim, 2.5 km run. If the rated water temperature is below 22 °C then it becomes a wetsuit-mandatory 1000 m swim and a single 5 km run. "Long course" distances are 2000 m swim and 10 km of running. Where the rated water temperature is low (around 16 °C) then the course may be shortened, and possibly cancelled.
Different national federations have their own distances and temperature rules, typically related to the acclimatisation of national athletes. For example the Icelanders will train/race at 10 °C whereas the BTF start at 12 °C. BTF aquathlons tend to be 750 m wetsuit-mandatory/optional and a 5 km run.
Aquathlons are most similar to triathlons, with the key difference being the lack of a cycle leg. The bike adds extra complexity for both the athletes and race organisers.
- Bikes must be transported to the venue, which can be logistically onerous for the athletes, especially for international events.
- The race director has to select a course that allows space for the bike leg, possibly including road closures.
- They can be run informally in local lakes.
Modern pentathlon is similar to an aquathlon in that both include swimming and running. But swimming and cross-country running are only two of the five events which make up the modern pentathlon, and these are held as distinct, noncontiguous events. Within the penthathlon sport the term biathle is also used for (training) races comprising swimming and running. These however contain distance stemming from pentathlon races, for instance 200 m swimming 3 km running.
Another sport derived from triathlon is duathlon, which combines cycling and running but has omitted the swimming part.