Jet Skis are certainly able to squeeze into narrow waterways, although you probably wouldn't feel comfortable scraping one's hull against a rocky riverbed. Steel-hulled jet boats are considerably tougher than Jet Skis, but they're not nearly as nimble. Alaska-based Mackinnon Marine Technologies' AlumaSki, however, attempts to combine the best of both worlds. It has the form factor of a personal watercraft, along with a one-piece quarter-inch-thick aluminum hull.
While the AlumaSki could be used in any number of places, it's intended particularly for exploring shallow, rocky rivers that are too narrow for a boat and too fiberglass-unfriendly for a Jet Ski. It has a very stable almost-flat bottom, drawing 6 inches (15 cm) of water when idling and 2 to 3 when moving – depending on the speed and payload.
Power is provided by a water-cooled, electronic fuel-injected Yamaha 1,052cc 4-cylinder, 4-stroke marine engine, that provides 110 hp. The craft is reportedly able to travel at up to 60 mph (97 km/h).
In order to keep the weight down, the non-hull parts of its body are constructed of thinner marine-grade 3/16-inch aluminum. It has a dry weight of 950 lb (430 kg), can carry up to 1,000 lb (454 kg), and is 12 feet long by five feet wide (3.7 by 1.5 m).
The AlumaSki is currently available for preorder, and should sell for US$24,995. It can be seen in action – albeit very briefly – in the following video.