The pool at a dock diving event is different for dogs that will jump into a lake no problem. I had an insande jumping dog. off of boats, off of docks, off of floating rafts, thru people on a dock, short ones, ones 7 feet off the water, didn't matter.
Took her to an outing probably the same as you did, and she jumped, but was a tad hesitant. It wasn't a launch it was a run up and jump, but not the all out launch she usuallly had.
Of course it was 3 hours of waiting and 10 bucks for the one jump, so I never went back to one again, but i'm sure once is all it would take for a dog that knows diving, to see that it was the same as it was used to everywhere else, and everything would be fine