If hippopotamuses can't swim, how did they land on Crete and Cyprus?

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?

Experts say that widely accepted models for the methods, patterns, and timing of the colonization and dispersal to several islands (e.g. Cyprus, Crete, and Madagascar) may need to be reconsidered.

"Although land bridge connections between these islands and the mainland are not currently supported by positive geological evidence, neither is there any contradictory evidence to exclude it," said Dr. Paul Mazza, author of a Lethaia article on the topic.