The man, identified as Jonathan Becker, 59 and from Arizona, was set upon by the crocodile on Friday while crossing a river between beaches in Tamarindo, in northwestern Costa Rica.
He managed to fight the reptile off and make it to shore, where local surfers helped him before he was taken to hospital.
The crocodile ripped flesh from the calf of his right leg, resulting in wounds so serious it had to be partially amputated, outlets including La Nacion and Teletica reported.
Teletica said authorities posted warning notices about crocodiles in the area after the attack, but it appeared some locals were taking them down to try to prevent the lucrative tourist trade fleeing.
