And they were still not out of danger if the enemy sub should dive in pursuit.

The less the enemy sub knew, assuming that it was hostile, the better off they were.

What makes you think we're the only ones sinking enemy subs?

"Think the enemy sub was searching for our Jupiter prober?"

I wonder if that's how the enemy sub blinds our sonar?

A thousand alert enemy subs ranging across our track.

There was an enemy sub out there, and he now had all sorts of noise from Chicago.

Still the enemy sub continued to close in like a marauding shark, finally passing Tom's craft.

Hell, they weren't even expecting an enemy sub here at the entrance.

The enemy sub showed no indication that it sensed its smaller shadow.