I have flown many airplanes in ground effects,(within one wing span of the surface) the air builds up under the front edges of the wings and hold it up above the ground, if you slow down a tiny bit it will land, if you make it accelerate a tiny bit it will gain altitude and break out of ground effects
The spruce goose never flew above ground effects, it was built mainly out of wood and it may have broken apart above ground effects, it wasn't design to fly very long as the proof of concept model