In a few months, Ben Lecomte will put his flippers and his snorkel on and get into the sea in Japan.
About six months and 8200km later, he plans to emerge from the water in San Francisco - having become the first person to swim across the Pacific.
He's got previous form, too. He swam 6000km to cross the Atlantic Ocean back in 1998.
En route, he will become a one-man floating, swimming laboratory, with researchers studying how his body reacts to extreme exercise. The results will also be used to simulate the effects of long-distance space travel.