Extinct — Charles Wilson

Six-year-old Paul Haines watches as two older boys dive into a coastal river…and don't come up. His mother, Carolyn, a charter boat captain on the Mississippi Gulf Coast, finds herself embroiled in the tragedy to an extent she could never have imagined.
TO THE DEEPEST PARTS OF THE PACIFIC…
Carolyn joins with marine biologist Alan Freeman in the hunt for a creature that is terrorizing the waters along the Gulf Coast. But neither of them could have envisioned exactly what kind of danger they are facing.
TERROR COMES TO THE SURFACE…
Yet one man, Admiral Vandiver, does know what this creature is, and how it has come into the shallows. And his secret obsession with it will force him, as well as Paul, Carolyn and Alan, into a race against time…and a race toward death.