I got these images second hand (perhaps third, forth, or fifth hand), so I can’t say where they came from or the date taken, but I think they are instructive for how they show how a vessel can be much more than it appears. Reportedly, this is a Russian trawler that was stationed off the Fleet Ballistic Missile Submarine base at Holy Lock, Scotland. That they were not there to fish was general knowledge, but I think the extent of modifications to the underwater body, particularly the apparent addition of torpedo tubes, may be a bit of a surprise.

Looking a bit closer:

 (Thanks to Robert Stoner and Tim Wind)