Into the Deep is a weak followup to Grimwood's excellent Replay. If you've read Replay, you will recognize the subject matter in this novel as the basis for the "Starsea" film in that book. Cetacean (dolphin/whale/etc.) intelligence was clearly one of Grimwood's passions, and the idea of humankind's first encounter with non-human intelligence (especially with creatures on our own planet) has the capacity to fuel a great novel, but this isn't it. I'm having a hard time putting my finger on what exactly disappointed me, but all I can definitively say is that I was never completely engaged by the story, and Grimwood's writing here seemed much less tight than it was in Replay.