|Twiggy the water-skiing squirrel|
I have wondered about this myself. In fact, for a long time I have thought about writing a post about Twiggy on this blog, but have hesitated to do so because I have very mixed feelings about this subject.
In general, I think it is wrong in most if not all cases to make animals perform tricks or stunts for public entertainment or amusement that they would not do of their own free will. I have demonstrated outside the Ringling Brothers' Circus protesting their treatment of elephants and other animals for this very reason.
Regarding the question of whether squirrels can swim, as Winkelhimer points out, the answer is that yes they can, but they prefer not to. According to the book Squirrels: The Animal Answer Guide by Thorington and Ferrell, gray squirrels will swim across streams and even large rivers if they have to during migrations in search of new food sources.
However, squirrels have never been observed riding water skis unless a human put them there.
The "About Us" page at Twiggy's web site explains how the original Twiggy (there have been several squirrels who have performed under this name over the years) was rescued after a hurricane and taught by Chuck and Lou Ann Best to water ski in the late 1970s.
I checked out a few videos from YouTube of Twiggy performing--most of the performances are done at boat shows, and take place in a wading pool with ankle-deep water. You can watch one of the videos below. My gut feeling from watching the performance is that the squirrel is getting onto the skis willingly, without being forced. I still have mixed feelings about this, but I don't see any reason to consider it abuse.