those wing-in-ground-effect (WIG) planes were meant for costal anti shipping defense. the one you posted, the Lun, weighs 400 tons - about the same as a fully loaded 747-400 - and flys@about 300 MPH, but ceiling is about 5 meters. the was a bigger one - 540 tons - named "The Caspian Sea Monster"
mpeg not sure, but maybe it was the heaviest thing ever to fly?