33 C.F.R. § 245.5
Abandonment means the surrendering of all rights to a vessel (or other obstruction) and its cargo by the owner, or owners if vessel and cargo are separately owned.
Hazard to navigation is an obstruction, usually sunken, that presents sufficient danger to navigation so as to require expeditious, affirmative action such as marking, removal, or redefinition of a designated waterway to provide for navigational safety.
Obstruction is anything that restricts, endangers or interferes with navigation.
Responsible party means the owner of a vessel and/or cargo, or an operator or lessee where the operator or lessee has substantial control of the vessel's operation.
Vessel as used in this part includes any ship, boat, barge, raft, or other water craft.
33 C.F.R. § 245.5