Martin Henry. Deep Whisper

Mark Castillo, captain of the submarine USS Pasadena, is tracking a brand new Russian missile submarine when sudden disaster tears him away from his quarry. Pasadena’s sonar watch has just detected a massive casualty aboard a Russian Victor-class fast attack — and the enemy boat is going down. Castillo races to the scene to help rescue the trapped sailors. He speaks with the desperate commander of the lost submarine — and is haunted by the Russian boat’s DEEP WHISPER.
Castillo will do just about anything to pull those sailors off the bottom, but the Russian government refuses his help — leaving him with a terrible dilemma.
Will he risk everything to help — or will he let his fellow submariners die?