Final Fathom — David E. Meadows

On the man-made island fortress known as Sea Base, enemies ar threatening from without and within. China, with its ships and sub marines swarming the area, seems poised to invade the island Taiwan. And when an escort of American and British planes ambushed by Chinese fighters, Sea Base prepares itself for showdown. But the battle may already be lost. An assassin ha infiltrated Sea Base to take out key personnel--one of their own crew may be a foreign agent.

Now, Sea Base will have to fight the enemy on two fronts if it i to survive...