Sometimes, when stories get passed from generation to generation to generaton.... details get lost.

In this case, the story of Noah's ark (as told in the bible) didnt seem to mention that they "may" have hit an iceberg, and some animals "may" not have survived the trip.. and you "may" notice the poor unicorn trying to swim to one of the lifeboats.

Like the Titanic, I guess they didnt have enough lifeboats.