Marine vessel
Marine vessel has the meaning given in 1 U.S.C. 3, except that it does not include amphibious vehicles. The definition in 1 U.S.C. 3 very broadly includes every craft capable of being used as a means of transportation on water.
Source
40 CFR § 91.3
Scoping language
The following definitions apply to this part 91. All terms not defined herein have the meaning given them in the Act.