You're probably thinking of Ground Effect Vehicles (sometimes Ekranoplans). The Russians built lots, not just as a concept, if you own a huge lake (not an ocean) they're somewhat practical for crossing it quickly. The Americans and Canadians (who also own some large lakes) have likewise built some of these.
The Ground Effect, as its name suggests, only exists near the ground, so in one sense you're "flying" but if the surface drops away you will fall too. Hence it's good on a lake or possibly open plains, but won't work on normal ground with rises and hills and so on, never mind buildings and trees.
I'd thought that there were only a few prototype Erkanoplans built, though it seems there actually was an operational fleet.
There's a particular larger model intended for defence purposes which saw only a single prototype, now abandoned.
The Soviet Navy ordered 120 Orlyonok-class ekranoplans, but this figure was later reduced to fewer than 30 vessels, with planned deployment mainly in the Black Sea and Baltic Sea fleets.
For water use, hovercraft tend to be more flexible. They still experience issues in rough water, and though they can cross flat unimproved terrain (beaches, swamps, snow, meadows), they perform quite poorly on slopes, particularly laterally, and generally have poor lateral stability, notably with high winds.
Hydrofoils accomplish much the same capability on water. Tracked vehicles on land. Not having to support your mass dynamically also helps. That said, hovercraft remain useful for military marine beach landings. And eels.
The Ground Effect, as its name suggests, only exists near the ground, so in one sense you're "flying" but if the surface drops away you will fall too. Hence it's good on a lake or possibly open plains, but won't work on normal ground with rises and hills and so on, never mind buildings and trees.