An in-browser competitive swimming simulation built on the one mechanism that separates swimming from every other water sport: whether the body is on the free surface or under it. A submerged body makes no waves and pays no wave-making drag; the decay is Havelock's exp(-2gh/U^2), derived in the app. All four strokes, the medleys and the relays, adjudicated against the World Aquatics Competition Regulations in force from February 2026, Part Two, over a drag model calibrated on published towing measurements. Entirely client-side: no model, no server, no API.

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