The Mac McDowell Mission Series

 Mac McDowell is the Officer-in-Charge of the Test Operations Group (TOG), a Top Secret Navy saturation diving team. He and his team of daredevil divers take on the might of the Soviet Union during the Cold War in harrowing underwater missions that challenge his team's abilities to their limit and beyond.

Each book stands on its own, but the books follow each other in sequence, each challenging Mac and his team to accomplish what appears to be an impossible mission.