Kraken vs. Megalodon — Eric S. Brown

All communications with the deep sea research facility code named Atlantis Alpha have been lost. DESRON 13, under the command of Commodore Blanton, has been dispatched to assess the situation. Blanton fears that the genetically engineered sharks of Project Megalodons have somehow managed to break free and turn on their creators. DESRON 13 however is destined for an encounter with an ancient evil from long before the time of man.