Undersea

What's more interesting than a story about two generational ships locked in decades-long battle with each other? The same, but in the depths of the ocean!

There's a lot of interesing stuff going on here - a look at generational conflict within a generational ship, the mechanics of a city-sized submarine, and some discussion of the human tendency to fight with outgroups, rather than work with them. There are also, in Thom and Ralla, some very interesting characters.

Unfortunately, the (to me) interesting stuff all takes place on the sidelines, and the main plot, with its cliched madman of a villain and boring love triangle, wasn't as nearly as interesting as the other stuff.