The diver was caught because someone was on the American side of the river and happened to see the man and called police.
The creative scuba enthusiast was toting eight pounds of pot when cops took him into custody dripping wet.
Police surveillance cameras also caught the scene and have wonderful pictures of the man swimming with a waterproof container that was keeping the weed dry.
Cops on both sides of the St. Clair River say the swim is a tough one, especially at night.
"If there’s a freighter coming through there, there’s no way for a freighter to stop. That’s a very, very dangerous thing to do," a customs worker told the Sarnia Observer.
A Canadian man who remains unnamed is high and dry in a warm little American jail cell.