Diver

A diver is a specialist who knows how to perform work under water in diving equipment.

Diving is scuba diving with special equipment.

Gidronaut, oceanaut, aquanaut — a specialist in deep-sea diving. Unlike ordinary divers, aquanauts are characterized by a long stay and work in underwater houses, laboratories or underwater apparatus. For decompression, hydro astronauts usually use a diving bell.

A man in diving gear could be mistaken for a sea monster or an alien, and his actions with lighting and other devices - with manifestations of an unidentified underwater object.