Many people forget or ignore the fact that objects float accross the oceans and land on shores thousands of miles away. Many people only think in terms of one only lifetime when thinking about possibilities.
What do you think the odds are that a dugout canoe from France or Spain floated accross the Atlantic during a period of, lets say, 1000 years? 5000 years? That's just one canoe. There were probably hundreds if not thousands of objects landing on beaches in North America that floated accross the oceans. Explorers may have been in those canoes but why do they have to be alive when they arrive? A canoe can carry a dead person just as far as a live one.
Sometimes the answer is right under our nose.