Yeah, I know about the Vikings. But there are some earlier and (to me) more remarkable voyages. Consider the case of the New World Monkeys.
Monkeys first evolved about 50 million years ago, in Africa. Somehow, about 30 million years ago, some of them (or maybe just one of them) managed to cross the Atlantic Ocean to South America. Recall that Gondwana, which included Africa, South America, Antarctica, India, and some other stuff split up about 180 million years ago (mya), with Africa and South America parting company about 130 million mya. The Atlantic was narrower than now 30 mya, but still at least 1000 miles wide. While it's possible that some mid-ocean islands existed, pretty extensive sailing, or rather rafting, was still required.
Alan de Queiroz has written a book about it, and has a shorter account of it here in The Huffington Post.
Many other creatures seem to have made similar voyages.
This story and others like demonstrate why evolution can't really be a predictive science - too much depends on extremely rare and probably one of a kind events.