Dr. Gareth Moore 
Ocean Puzzles [PDF ebook] 

Ahoy! You’re an accidental pilot aboard a submarine that’s sinking fast! Solve the puzzles to take control and navigate safely back to land. Devised by an expert on brain training, these mental gymnastics-and a friendly dolphin-will see you through your ocean adventure! You can’t skip a puzzle, but there are hints to help and full answers to get you on your way.