A 21-year-old man is dead after a personal watercraft collided with an unknown obstacle overnight in the Thousand Islands region of the St. Lawrence River.

Ontario Provincial Police and paramedics responded to a report of the crash just before 6 a.m. Sunday.

It happened among a group of small islands west of the Thousand Islands Bridge, between the mainland and Hill Island. The bridge is east of Ivy Lea, Ont.

Two people were on board. The passenger managed to swim to shore and get help. The driver was found in the water with no vital signs.

Police offered few other specifics, including what object the boat struck.

The OPP is asking anyone who witnessed the collision or has any information to call the Leeds County OPP at 1-888-310-1122 and refer to incident E241337329.