In simple words: Drowning and submersion resulting from an accident on board a watercraft, where the watercraft itself was not involved in an accident.

Drowning and submersion due to accident on board watercraft, without accident to watercraft. Excludes1: civilian water transport accident involving military watercraft (V94.81-), drowning or submersion due to accident to watercraft (V90-V91), drowning or submersion of diver who voluntarily jumps from boat not involved in an accident (W16.711, W16.721), fall into water without watercraft (W16.-), military watercraft accident in military or war operations (Y36, Y37)

Example 1: A passenger on a ferry falls overboard due to a sudden lurch of the vessel and drowns., A child playing on the deck of a houseboat slips and falls into the water, resulting in drowning., An individual fishing from a small boat loses balance and falls into the water, unable to swim back to the boat and drowns.