We went on them a couple of times: once just to see what it was like, and once with visitors to London.There was a slipway next or near to the MI6 building, Vauxhall. One boarded via steps on land, then it drove down into the Thames. Fun to do once, or twice; the commentary was inaccurate, perhaps supposed to be amusing ... but might be puzzling for tourists.
Michael Ixer ● 38d