Marine flatworms are some of the ocean's most beautiful of those creatures that can be encountered by divers, snorkelers or simply lovers of marine life under water or in the intertidal zone. They are relatively simple animals with soft flat bodies. In this book we will focus on the free-living highly diverse marine flatworms of the order Polycladida. Often confused with nudibranchs, they are falling under the completely different phylum platyhelminthes (Platyhelminthes, Greek "platy": flat; "helminth": worm.) The book covers the region from the Red Sea, East and South Africa to Hawaii, Marshall Islands and Guam. Inside the book: Over 1300 full color photographs of 580+ species; Particular attention was paid to color variations; Live photo of hundreds of species have never before appeared in field guides or popular books; Convenient pictorial guide at the beginning and index at the end of the book. The book contains photographs of most of the recently described Indo-Pacific flatworms, some of them are represented by holotypes.