The term knots per hour is used in defining acceleration. Bit of trivia
knowledge I learned once upon a time. Actual Speed is Nautical Miles Per
Hour (relating to the water or relating to the ground). The other
definition is: "Depends on whom I'm after . . .or trying to get away
from.!"

MST

Bubbles, what about surfing?

Never heard of the downhill slide...it's a sailing term.

I've also heard of boats "heaving" which they don't do either.

RB