From the back of the book:
A Treasury of Nautical Lore!
No place offers mor eadventure than the ocean. No dungeon is as deep, no jungle is as full of exotic and dangerous life. Most folk spend their entire lives on dry ground, unaware that entire civilizations thrive beneath the waves. Seldom do PCs venture into the depths, but when they do, they discover wonders of which they never dreamed. The ocean offers a realm of adventure that is at once alien and appealing. Strange things exist down there, as perilous as they are compelling.
Dead Man's Chest lays bare the ocean and its denizens. Within these pages are detailed rules for ship travel, as well as guidelines for underwater exploration, and three complete maritime adventures. At last there is a comprehensive source for sailing and the sea - packed with over 100 new magic items, monsters, feats, prestige classes and spells.