Man overboard dies after hit by own boat

A man is dead after he was hit by his own boat after falling overboard near WA's Rottnest Island.

The man was one of two men on board a boat when they encountered rough seas northwest of Cathedral Rocks around 6.30am on Monday.

Both men fell into the water and one of them, a 37-year-old from Wembley, was struck by the boat. He suffered critical injuries.

The men were rescued by a nearby vessel, but the man died from his injuries, police say.