I'm not sure that you're better off in the water, even if the boat is the target. Water is incompressible, so it transmits explosive force well. Maybe if you can get far enough away.
Blast fishing, fish bombing, dynamite fishing or grenade fishing is a destructive fishing practice using explosives to stun or kill schools of fish for easy collection.
Water masks their heat signature. So getting into the water while the boat is still moving and swimming away from the burning boat may be a good option to hide. They need to stay underwater for as long as possible though.