This mug is designed to look like a diver in an old-fashioned dive suit holding a mermaid.

From Forbidden Island:

"The Green/ Copper oxide glaze of our official 17th Anniversary mug, designed by BigToe Art and produced by Munktiki. Glaze represents oxided mug 'pulled from the sea'. Mug stands 9 inches tall and holds 20oz of liquid."

There was also a second edition released simultaneously in a full color glaze.