The Sea to Summit Triathlon is a largely self-supported race consisting of:

a 1.5 mile swim in a tidal river connected to the Atlantic Ocean
a 91-95 mile bike ride (depending on course variations) from Maine into New Hampshire, following roads of your choosing, with 6000 feet of climbing
a strenuous five mile run/climb up the tallest mountain in the Northeast: Mount Washington, with 4300 feet of vertical gain in altitude