Travesía a nado La Isla is an open-water swimming race in San Sebastián, in Guipuzkoa on Spain’s Basque coast. It is listed for late August, although the published date is not yet confirmed, and Runedia classifies it simply as a swimming event rather than a running race.
The event has reached its twelfth edition, so it is not a one-off swim. The listed distance is not homologated, and the organizer page also marks it as connected to a cup, championship, or circuit, though the public listing does not name which one.