From Bulbapedia, the community-driven Pokémon encyclopedia.
Map of the Triathlon route. Starts at the school (center right), then goes to the forest (top), continues to the lake (bottom), then finishes at the school.
The Pokémon Triathlon (Japanese: ポケモントライアスロン Pokémon Triathlon) is an anime-exclusive competition held in Sinnoh. The event concludes a student's participation in Professor Rowan's Pokémon Summer Academy, which is then followed by a bonfire. It was featured in One Team, Two Team, Red Team, Blue Team!.
The Pokémon Triathlon consists of a three-part race where the competitors do not use any of their own Pokémon, but instead borrow those of the school.
Students start at the academy simultaneously. When the race begins competitors race to a checkpoint to borrow one of the Pokémon available and then are required to ride on the Pokémon to the next checkpoint through the woods. When the participant reaches the second checkpoint the participant then needs to return the first Pokémon the participant borrowed in exchange for a Water-type Pokémon, which the participant then needs to ride across the lake. Once the participant gets across the lake, it is a dash to the finish line located back at the academy. First place earns 50 points, second place earns 30 points, third place earns 20 points, and all of the remaining teams will receive 10 points a piece.
This listing is of the known Pokémon used by the students during the triathlon:
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