by the leash and board. Many people with life jackets drown when thrown from a raft and their foot gets stuck on a rock bec they either try standing up or they aren't properly prepared for being ejected into the water.
Nose and toes to the sky anytime you're thrown into a river. Never stand up. Always wear a life jacket. Don't tie yourself to anything. The river will let you go eventually. Go for the eddy.