Terrestrial animals that make it to remote islands like the Galapagos are good example - the best current theory is that the got there by riding natural rafts of storm debris (fallen trees etc.). The number of founding individuals is estimated to be very small, because it is a freak random event that any make it all all.
Until driven extinct in the 19th century, there were many islands with giant tortises besides the Galapagos - particularly in the Indian Ocean. The island of Aldabra still has them. Tortises seem to raft well, and can survive without water for a while which makes them good candidates.