The Hippie Leader is a large, bearded Caucasian man, and the Captain of the S.S. Friendship.
During the events of The Beach he, along with the rest of the Hippies of the S.S. Friendship, travel to the Gulf of Santa Catalina to stop "the worlds largest trash barge" from dumping 60 thousand tons of radioactive waste into the waters.
He appears to be a terrible leader, unable to properly rally his people and simply allowing them to do whatever. They likely would have accomplished nothing if not for Dan and Chris offering to help them. Even then, he is powerless to fight back when Dan betrays them, proving his terrible leadership once more.
He is last seen outside of Casa Paradiso at the end of the episode. For reasons unknown, he and the rest of the group have set up camp just outside.