Burial at sea is traditional in many navies particularly in wartime.
Burial at sea is the disposal of human remains in the ocean, normally from a ship or boat. It is regularly performed by navies, and is done by private citizens in many countries.
Burial-at-sea services are conducted at many different locations and with many different customs, either by ship or by aircraft. Usually, either the captain of the ship or aircraft or a religious representative (of the deceased's religion or the state religion) performs the ceremony.
In wartime, attempts are made for burial at sea to follow the same procedure as for peacetime burial at sea, although a ship on a combat mission may not have all the necessary resources available.
Given that cremation is not possible and submergence is acceptable, burial at sea is the most obvious choice.