Deep Black: Darkzone

In a secluded headquarters on the other side of the globe, a terrorist mission is underway - a plan to set of an underwater explosion so great, with such a hellish force, that it could shift the very foundation of the earth's surface, causing untold calamity and world-wide disaster. The terrorists call it "God's Revenge"A nuclear weapon has gone missing. Small in size, it packs up to ten times the kilotons that exploded over Hiroshima.
It's now in the wrong hands, ready to detonate a world war of unfathomable proportions. In the top-secret headquarters of the National Security Agency, a small cadre of special agents form Deep Black, a team designed to bring a techno-edge to covert operations and eliminate the cyber-threats to world peace. This is Charlie Dean's world - an NSA ex-Marine sniper now enlisted to stop the unthinkable.
But when his suspicions of a traitor in his shadow become frighteningly true, Dean's race against time could mean the end of the free world.