From publisher blurb:
The tenth volume in our Mythic Monsters series, Mythic Monsters: Sea Monsters brings you a dozen and one maritime menaces ready to leave your PCs scurrying for the safety of shore. Here there be monsters indeed, from treacherous sea hags and malevolent devilfish luring sailors to be devoured or enslaved to titanic terrors of the deep like the sea serpent and dragon turtle that hunt out of instinct and hunger but pose no less a peril. Size hardly equates to stupidity, however, as clockwork leviathans are relics of ancient and advanced civilizations still following the residual programming from ages long past, while krakens are beings of unfathomable intellect and ineffable evil. Still, a few citizens of the sea might lend a sympathetic flipper if approached the right way, like the selkie and the seaweed leshy. As if these mythic sea monsters were not enough, Mythic Monsters: Sea Monsters also explores an assortment of feats uniquely suited to aquatic creatures, helping to lend a legendary touch to creatures from the briny blue. The 13 sea monsters contained herein, ranging in CR from 3 to 22, are updated for the mythic rules, and when we say updated we mean complete stat blocks, yes, but more than that every one has its own unique and exciting new mythic abilities, from a mythic draugr crew's phantom broadside and ship of the damned to the ionic meltdown and orichalum alloy of a mythic clockwork leviathan!