It's one of Paizo's excellent adventure paths, giving a fun and varied mix of roleplay, exploration, crawling and all-around good time. Also, it's heavy on the water and ship adventure theme.The first savage tide has already touched the mortal world, yet none who live today recall this time of red ruin. Unleashed from the cruel heart of a fell seed known as a shadow pearl, this savage tide swept over an ancient city perched atop the crown of a remote island. The tide transformed beggar and noble, merchant and thief, resident and visitor into feral, ravenous fiends. The fruits of centuries of labor came crumbling down in a matter of days, and when survivors tried to stem the tide by destroying the pearl, the resulting blast of power sunk the city into a boiling lake of death. Through it all, the Abyssal architect of the savage tide watched, taking pride in the ruin. Then the tide's final ripples had faded, what was left became known as the Isle of Dread.
Now, after a thousant years, the true masters of the Isle of Dread look upon new targets, cities beyond the horizon, compelled by the hateful will of their demonic lord Demogorgon to prepare for the coming glory. This time, the doom will not be limited to one hapless city. This time, all of civilization waits unknowing on the shore, blissfully ignorant of what the incoming tide brings in.