I used to love it when the old Sydney hydrofoils where operating, when the swell through the heads really got up, they would cancel the ferry service (the ferry's were fine...is just they did not like the passengers getting washed of the decks).
But the hydrofoils where enclosed, and their operating speed was 30+ knts (and could not really slow down much as they would fall off the foil)
30 knts through a 3m swell , for the cost of a few bucks was better than any Luna park ride
