I see a lot of commentary on the Interwebs that operating ground effect vehicles doesn't require a pilot's license. However, many GEVs can reach an altitude of 20 feet and are supported solely by aerodynamic forces, and thus are both aircraft and airplanes under part 1. The way I see it, if a GEV is operated by and occupied by a human (i.e. not a drone), operating a GEV requires a pilot's license.
Part 1: Aircraft means a device that is used or intended to be used for flight in the air. Civil aircraft means aircraft other than public aircraft. Airplane means an engine-driven fixed-wing aircraft heavier than air, that is supported in flight by the dynamic reaction of the air against its wings. Crewmember means a person assigned to perform duty in an aircraft during flight time.
§61.3 Requirement for certificates, ratings, and authorizations.
(a) Required pilot certificate for operating a civil aircraft of the United States. No person may serve as a required pilot flight crewmember of a civil aircraft of the United States, unless that person:
(1) Has in the person's physical possession or readily accessible in the aircraft when exercising the privileges of that pilot certificate or authorization—
(i) A pilot certificate issued under this part and in accordance with §61.19;...