Beyond 'Fun Size', kin to speed-boats & hydrofoils, you have the problem of wave height.
Yes, such as the 'Caspian Sea Monster' could hop sand-banks and fishing boats but, like big sea-planes --Think 'Sunderland' or the JDF's sea-patrol-- GEVs need mild sea-state to land / take off. Worse, like big hovercraft, GEVs cannot fly above weather...
A proviso:
Mega-GEVs would be okay, snag is they'd need nuclear power, be it fission or, safer, fusion. So, perhaps, early 22nd Century ??
Also, IIRC, DARPA propose the 'Liberty Lifter', a big, dual hull 'flying boat' that would be good to ~10,000 ft, yet significantly extend over-water range by flying at ~250 knots in 'ground effect'.
DARPA announced it is moving forward with plans to develop an entirely new class of flying boat for use in amphibious military operations.
thedebrief.org
FWIW, IIRC, many 'Sunderland' sub-hunters were based at a Scottish loch, with convenient 'prevailing wind', plus a 'rode' that provided waves of convenient height to easily 'unstick', yet not big enough to damage...
Speaking of big hovercraft, our family once crossed English Channel on one of those big hover-ferries. The sea condition was
deplorable. Route crossed Goodwin Sands. I repeatedly saw beige 'beach' along wave troughs, was very, very glad I was not a sailor beset on that notoriously lethal bank. Wave length and height were often enough to 'vent' air-cushion, which meant the entire craft tossed, rolled like any short ship in steep sea. Cabin conditions akin to wide-body jet meeting 'Clear Air Turbulence'. Ick. We often had air-gap between butt and seat. Even those passengers
not sea-sick were '
significantly impaired'. We lost much of the time we'd saved over a ship-crossing by having to park-up, wait for our wits and guts to settle. Then, re-pack car to locate and replace everything that had been tossed around...
FWIW, the following year, the craft had been lengthened, significantly improving ride,
and seat-belts fitted...