On many Cretan beaches you will be offered various kinds of active recreation. Windsurfing, trips on "bananas", catamarans, jet skis (10-15 EUR, the longer you ride, the cheaper the hour of rental) are especially popular here.
Less often tourists order in Chania wakesurf, wakeboarding, water skiing (20-45 EUR for 10 minutes).
The cost of other "exotic" types of entertainment on the water reaches 50-70, or even 100 EUR. But you can bargain and get a discount. Cretans' accommodating attitude depends on the location of the beach, the season, the number of people and other factors.