Matthew Moseley’s open-water swimming feats are so impressive, even the Hunter S. Thompson took notice.

“Gonzo swimming” didn’t exist until Matt Moseley combined his quixotic endeavors with Hunter S. Thompson’s unrivaled wit. Far from the merman figure one might conjure when imagining who could swim cage-free across the Caribbean Sea — from the U.S. Virgin Islands to Puerto Rico — Moseley presents the jovial visage of an everyman.

But his ruddy cheeks and easy manner belie a man who’s dived headlong into stormy seas not just literally, but also as an agent of social change. From the worsening water crisis choking off America’s waterways to high-profile murder cases, Moseley’s aquatic antics seem very much in line with his everyday convictions.

Moseley’s latest feat, swimming the length of the Green River, is part of his ongoing efforts to address the water plight of the rivers of the American West. It’s also the subject of an upcoming film from American Rivers.