"The Merlin Effect" by T.A. Barron (Preowned Paperback)

Kate Gordon accompanies her father on a quest for a sunken Spanish galleon that contains a treasure beyond price--a mysterious drinking horn which legend states may have been responsible for Merlin's death. Now, to save her father's life, Kate must enter an undersea world of bizarre creatures and terrifying foes, and succeed where Merlin failed.

This is a preowned paperback in good condition.