It appear that the Aqua Duck will not be much of a thrill ride compared with on-shore water slides which use the water coaster technology.
Other than the loop off the side of the ship, which won't be a big thrill unless you're afraid of heights, you're just riding on a tube, in a tube...with a couple of very small drops, followed by the water jets to propel you further along. Maybe it will be faster than it looks...and you can't really see the "mammoth drop" in the photo...and according to the disney website:
AquaDuck is a thrilling "water coaster," whose entrance is on Deck 12, Aft aboard the Disney Dream. In a cruise industry first, Guests are propelled at high speeds from Deck 12, Aft through an acrylic tube on a breathtaking journey up, down, around and off the side of the ship, through the Forward Funnel andfollowing a mammoth dropinto a lazy river.
Developed by the Disney Imagineers, this elevated water coasterthe first of its kind at seatravels 765 feet and features an exciting 4 deck drop. It was designed for Adults and Children at least 48" or taller.
AquaDuck affords breathtaking views of the ocean and ship belowthat is, if you're brave enough to keep your eyes open during this exciting ride! It also offers a bird's-eye view of the exciting new pools available to family, kids and adults on the Disney Dream.