These catamaran inflatables fall into two categories: Those that are designed for stability as a tender vs. those that are designed for performance. The first category is great for diving and is easily boarded over the front.

The latter category is differentiated by having a stronger structure to handle higher horsepower motors, and by an inflatable small-diameter tube beneath each pontoon to act as a mini-keel that allows them to get up on just the smaller tube at high speeds and the keel also improves stability/tracking in high speed corners. They corner like slot cars. A friend of mine got one set up with a 50 hp Yamaha 2-stroke with racing prop -- it could hit about 50 mph and the power/weight ratio is pretty extreme. My sons played around with it for an hour or so and said the cornering/acceleration forces are insane. I took it out for a spin also but needless to say I was a lot more conservative as a driver. I was afraid I'd get thrown out if I pushed the cornering abilities.

Here is a link to a video to some racing footage: http://wn.com/xtreme_thundercat_racing