Looks like fun-
Twin-Turbo Powered Jet Boat Ride - One ($29), Two ($55), Four ($109) or Six ($159) People at Downunder Jet, Sydney Harbour (Up to $360 Value)
Get this Groupon Discount bargain! for Jet Boat Ride on Sydney Harbour from Groupon!
That does look fun! I see them on the harbour a lot and have thought about it. from their youtube site:
See a spectacular jet boat experience on Sydney Harbour on the DOWN UNDER JET boat . See the great footage of SPINS, BRAKE STOPS near the Opera House, Circular Quay and Sydney Harbour Bridge in SUPER SLOW-MO.