The Enduroman Arch 2 Arc Ultra Distance Triathlon starts at Marble Arch in London and ends of the Arc de Triomphe in Paris. The timed triathlon involves an 87 mile run from Marble Arch in London to Dover, a 21 mile swim across the English Channel, foolowed by a 181 mile cycle to the Arc de Triomphe.
Only 43 Athletes have ever finished and only 5 have managed it without a wet suit.
About - Enduroman
Enduroman - Wikipedia
Do you know of any other very ddifficult ultra-triathlons.