Yesterday We Saw Mermaids

This is NOT a mermaid book! (The title is a quote from Christopher Columbus's diary.) In this disturbing book, mythical king Prester John's ship is racing against Columbus to the New World. If he gets there first, all of the mythical creatures such as unicorns, fairies, pixies, selkies, etc will be saved and stay on earth. If not, they will be gone forever. This ship also carries a pregnant girl. She may or may not be a virgin, and may or may not be carrying a Savior, or just a human baby.