An airboat in the Grassrivers with Airgator Airboats and Airboat 09 printed on a panel in front of its propeller cage, in Rockstar's screenshot Grassrivers 01.
Rockstar Games
Three mud-covered locals pose on the boat with a dead alligator and a wildcat in Rockstar's screenshot, which Rockstar's Only in Leonida page describes as "an airboat in the Grassrivers." A metal panel in front of the propeller cage reads Airgator, with Airboats in small letters below it and Airboat 09 underneath.
The name is printed in Rockstar's own screenshot. Rockstar hasn't said whether Airgator is the boat's maker, its model or the outfit that runs it. Airboating is one of GTA 6's side activities.