If hippopotamuses can’t swim, how can some be living on islands?

15 septiembre 2014

There is no published account where hippopotamuses are demonstrably shown swimming or floating at the surface of any body of water. But if they can’t swim, how did they reach and colonize islands?
http://feeds.sciencedaily.com/~r/sciencedaily/~3/0BKfD4uOhoU/140915120757.htm