The Marathon Swimmers Federation (MSF) is a non-profit organization dedicated to advancing solo long-distance open water swimming through projects like the LongSwims Database, which contains over 100,000 swims from 1875 to present. It offers swim ratification, GPS tracking, and a calendar of public 10km+ swims, while also maintaining widely adopted rules for unassisted solo marathon swimming.
AI named Marathon Swimmers Federation from December 2025 to September 2026.
Brand page for ultraswimming-org