Grimsby is a ruinous, underwater city. It was once a Raft City (and before that a seaport in Lincolnshire, England), but was sunk by the Anti-Traction League in the Iron Winter of 919 TE. After it sank, it was found and re-purposed by Uncle and the Lost Boys who used it as a base for their crimes. However, after the publication of Predator's Gold by Nimrod Pennyroyal people became aware of the Lost Boys' criminal activites and Brighton started actively hunting them down. The city was bombed by Brighton, leaving it completely waterlogged and useless.

Grimsby was known for being a predator city, and feared in the North by many smaller towns. It also seemed by extremely unpopular with most of the Northern raft cities, perhaps because of being such a successful urbivore.