I am wondering at what altitude does a hovercraft become an airplane according to the FAA. This craft has enough aspect ratio that it looks like flying to me. There isn't much difference in flying low over water versus over land except over water you might have to hold your breath longer. We do in fact fly very low over land but you will notice that true low wing ultralights are somewhat uncommon. At low wing loadings its easier to catch a wingtip on landings.
I tend to believe that once the craft is higher than it's width it's difficult to call it a ground effect vehicle. Also once that high you are probably wasting a lot of weight and horsepower in the "downblower". Simply cut the engine size in half and install wheels or floats.
None of this is an issue if it's a FAR103 ultralight in the USA. Anything under the weight speed and fuel is allowed. A larger craft flown out of ground effect might require and airworthiness certificate in the USA.