I read again all the clues,
(built by Vauxhall under Wayne Cherry's lead
one-off prototype design study for a potential production car, Viva-based.
Not electric, amphibious and not a Golf Cart, a dragster, a zoo safari car, a train tractor, a glider puller, a rental car for sea-resorts, a tender, a gift for personalities, a parade car, a test car, a movie-tv serie car, a touring car for visiting the factory, a popemobile,
Not a beachcar (but close) and designed for specific markets)
The only time when we seem to be close was when there was the sea involved. That plus the 'specific market' hint.
If I have to connect this with the 'vehicle segment' clue... I'm lost!
Could it be a car for people without a licence because they are lost in an island?