2026.2 RULES
Rules and ratification
BISA's rules follow the tradition of unassisted marathon swimming and are aligned with the Marathon Swimmers Federation. This is a summary of the 2026.2 rules; in case of doubt, the current version of the rules applies.
Ratification
BISA ratifies swims by swimmers registered with the association who complete the route they set out to swim, escorted by a boat and pilot registered with BISA and accompanied by an official observer, following the rules and with the swim fees paid.
The swim starts with a horn, with the swimmer's whole body out of the water on the start beach, and ends when the swimmer clears the water completely on the finish beach, with another horn.
Standard equipment
Only standard equipment is allowed: one porous textile swimsuit (for men, between waist and knee; for women, not beyond knee, neck or shoulder), one latex or silicone cap, goggles, earplugs, nose clip, sunscreen and grease. Safety lights for the night, a simple timing device and nutrition passed from the boat are also standard.
Neoprene of any kind (suit, cap, boots or gloves), fins, pull buoys, music or devices that relay information to the swimmer beyond time of day and elapsed time are not allowed. Every BISA route is a no-wetsuit swim.
No contact, no drafting
The swimmer may not make intentional supportive contact with the boat, any object or the crew at any time, and may not draft behind the escort boat or a pace swimmer. Swimming alongside the boat is fine; sitting in its bow wave is allowed only while feeding. Feeding equipment may not support or tow the swimmer.
Pace swimmers
Solo swimmers may be joined by a pace swimmer for up to one hour per entry, with no fractional hours and one hour between entries. The number of entries depends on the route: none on the 12 km, one on the 16 km, two on the 22 km, three on the 25 km, four on the 37 km, five on the 48 km and six on the 76 km. There are no pace swimmers in relays.
Relays
Teams of two, three or four swim successive legs in a fixed order and interval: 30 minutes on the 16 km and 60 minutes elsewhere. Changeovers happen in the water, with the next swimmer approaching from behind, within five minutes of the scheduled time. If a team member withdraws or cannot swim, the swim is not ratified.
Who decides what
The observer documents the facts of the swim, interprets the rules and keeps the official time. The escort boat pilot is the final authority on everything else and may end the swim at any time for safety.
The call to embark depends on the sea forecast. BISA does not confirm a swim when the forecast for the open-sea stretches shows waves above 1.2 metres or sustained winds above 10 knots.
Crew on board
Besides the swimmers, at most two support crew may board, aged over 14 and directly involved in the swim. The boat is dedicated to the attempt, not to sightseeing.
Go deeper
- Marathon swimming in BrazilOpen water marathon and ultra marathon swims on Ilha Grande, Brazil: seven routes from 12 to 76 km, solo or relay, under MSF-aligned rules with escort boat and official observer.
- English Channel and Oceans SevenCompare BISA's Ilha Grande routes with the English Channel and the Oceans Seven: distances, no-wetsuit rules, escort boat and observer. Long swims in Brazil during the northern off-season.
- Marathon swim preparationWhat BISA requires for a marathon swim on Ilha Grande: medical and training certificates, feeding from the boat, pace swimmers, crew on board and swimming through the night.
BISA · ILHA GRANDE
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