Pacific Vortex is by Clive Cussler. The first book in the Dirk Pitt series. Dirk is a deep-sea expert and treasure hunter. When a note in a bottle washes up on the beach where he happens to be sunning, Dirk finds himself drawn into the hunt for a missing Navy sub lost in a mysterious area call the Pacific Vortex - the Bermuda Triangle of the Pacific. He only has a limited amount of time to retrieve the sub before the Navy fires a missile to destroy it; with time running out Pitt must descend into a secret underwater world from which he may never return.
Ratings: Adult - 8 out of 10 - P (profanity) - AC (mature thematic content) - V (violence).