X6: Quagmire!
X6: Quagmire! is Merle Rasmussen's 1984 adventure module for Expert play in Dungeons & Dragons, levels 4-10. It takes its cue from the southeast coastal edges of the maps from X4 and X5, both coastal. Thus is detailed what's between them to the south: fucking fantasy Florida. It's another wilderness-terrain showcase like Isle of Dread.
There's two descriptions of Slagovich from X5. First its harbour, "rocky" and "deep". Further in, setting J tells about its market. The northern part of the map overlaps X4's Burning Waste and Barren Plain, repeated here with a little extra, so this module can be used to supplement that one. (X4's plot did explain why that party didn't just sail over to Hule in the first place.) Then there are two shitpot towns Mule Beach and Sea Camel, spanning the neck of the Serpent peninsula.
None of this local colour has anything to do with the adventure's plot. Thanegia, the massive island to the south, doesn't even have keyed encounters. It's pure Gazetteer. Not that there's anything wrong with that.
The titular Quagmire is the setting's Miami, at the east edge of the Shallow Sea off the southern edge of the peninsula. It's a spiral tower rooted on the ocean floor, "floor" being a relative term because the island is sinking. "City" is relative too: the ruler is a dying man named Molariah, and his subjects number all of 42. The city's under a lizardman siege; they know that time is on their side. The plot, then, is to break the siege as to lead the Quagmarines to some other site. Since there's absolutely no civilisation here and since the Quagmarines haven't a ghost of a chance in the swamps, they'll need to find a site just like the last one. That other site would be Thanopolis, other side of Thanegia.
And we're not kidding. Paper space was at a premium, for X modules, and Rasmussen has already spent 21 pages on wilderness. So he just uses the same spiral-city map to detail both cities: Quagmire itself, not long for our world; and Thanopolis, which is monster-infested (in fact, "Death City" in Greek, which the author may or may not have known).
Then Rasmussen adds a third, already-sunken city called Yavdlom now inhabited by gazurtoidsmermen who hate airbreathing scum. There are maps in Thanopolis to point the way to Yavdlom - other end of the Shallow Sea. There's a ruin for a fourth city as well in the peninsula. There form no part of the mainline plot so, here's the DM springboard for future adventures.
Molariah promises the party that his people "will proclaim you leaders". If the party does clean out Thanopolis the twelve Quagmarine men will instead buy you off with their treasury. They don't want you Alpha'ing their 14 women like these wimps deserve. But you can totally rule 'em (if you have Companion Set) and cuck 'em. Maybe the whole Thanegia island that the new city's on, too.