Burial at sea describes the procedure of disposing of human remains

Body

With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...

 in the ocean, normally from a ship or boat. It is regularly performed by navies, but also can be done by private citizens in many countries.
Burial at sea services are available at many different locations and with many different customs, either by ship or by aircraft. Usually, either the captain

Captain (nautical)

A sea captain is a licensed mariner in ultimate command of the vessel. The captain is responsible for its safe and efficient operation, including cargo operations, navigation, crew management and ensuring that the vessel complies with local and international laws, as well as company and flag...

 (or commanding officer) of the ship or aircraft or a representative of the religion performs the ceremony.

The ceremony may include burial in a casket, burial sewn in sailcloth, burial in an urn, or scattering of the cremated remains by ship.