They were mainly old Romeo-class diesel boats, long past whatever prime they'd once had.

The 1971 diesel boats forever pin would be an example of this type.

Must be a diesel boat since it was so quiet.

We may very well run into another diesel boat hiding out here.

And one diesel boat, tentatively identified as Chinese of all things.

"So what are they doing with the diesel boats?"

Just how important are new batteries for a diesel boat?

My first guess would be a diesel boat on batteries, and close.

Even if we find a diesel boat in the Pacific now, we have no grounds to stop it.

But the most iffy part of the plan was that the diesel boats couldn't cover great distances quickly.