Normally, animals are only able to mate with those of their own species. But there are some that are so closely related to others that it is actually biologically possible for them to create viable offspring. It’s extremely rare in the wild, and tends to only happen in captivity… but even then the odds of achieving a successful birth are remote.

This doesn’t mean it never happens, however, and true hybrids are some of the most interesting and unusual creatures you’ll ever see roaming the world. From underwater wonders to powerful farm animals, here are the top 15 most Rare Cross Breed Animals.