New for 2026, the Gaelforce Great Marathon Swim series - a 12km river ultra along the mighty River Shannon and an 8km of Atlantic intensity in Killary Fjord. Shaped by natural flow, exposure and conditions, each course offers a demanding marathon swim event in a standout destination in the west of Ireland.

Aimed at elite marathon swimmers and ambitious open-water competitors seeking distance progression and internationally distinctive courses, these events demand preparation, resilience and confident open-water skills.
 
Experienced organisers, professional safety and medical teams and excellent athlete facilities deliver a focused, high-quality race environment.

A dedicated expert safety & training support service is also available for swimmers preparing for Gaelforce Great Marathon Swim events.
 
Enter one, both, or integrate into the Gaelforce Great Swim Trilogy as part of a focused endurance season.