Just beginning work on a Sea Castle - part of the five elemental temples series (well, they're not all temples - in fact, they're tombs, really...)
Anyway, here's just a little of what I've got.
Palace of the Water Spirits
The Coming Darkness
The Five Elemental Tombs/Temples/Castles/Strongholds...
An AD&D/OSRIC adventure for 4-8 Characters levels 8-10
by William R. Beatty
The Palace of the Water Spirits is build on an island that was an ancient site of Elemental Water worship. In the center of this small island was a pool and a fountain beneath which was a small complex of rooms which led deeper to more levels of dungeon. When the forces of good defeated the Elemental Gods and imprisoned them, the lower levels of this complex were sealed. As the land became more settled and people forgot about the ancient elemental gods, a fortress was built on this site to protect shipping lanes from river pirates and to aid in protecting the kingdom.
Recently, the fortress was invaded from below by hordes of Kuo Toa and other creatures from the deep darkness. The garrison was quickly overpowered and slaughtered or enslaved and taken to the deep darkness. One lone soldier escaped, badly wounded (see encounters below).
The party is contacted by the local ruler (king, baron, duke, mayor, whoever) to investigate why there has been no contact from the fortress recently.
Adventure Summary
The party is asked to find out why there has been no contact from the River Fortress for some time now. The fortress has been overrun by Kuo Toa and other creatures at the direction of a Water Wraithlord. The Water Wraithlord serves the elemental god Shallalath, evil elemental god of water. The Wraithlord ultimately wishes to raise the Elder God of Darkness and Chaos, he who must not be named. Calling forth Shallalath from his watery prison is one step in releasing all the elder elemental gods. Deep beneath the River Fortress the Wraithlord is working on a complicated and dangerous ritual to raise the sleeping water god.
As the party searches the overtaken fortress, they will find clues as to the nature of what the Wraithlord is trying to do.
Outdoor Encounters
Random Encounters
Water Weird
Water Elemental
Eye of the Deep
Sea Hag
Kelpie
Kraken
Water Mephit
Water Naga?
Sirine
Nixie
Aboleth
Bullywug
Kopru
Sahuagin
Squid
Octopus
Sea Drake?
Crab
From Monsters of Myth
Crab, Giant Fiddler
**Floating Mound – put a couple of these in the water around the castle patrolling...
***Giant, Sea – could have a couple of these protecting an area. Trouble is they're pretty much underwater only...
Glow Jelly
Jellyfish, Giant Moon
Navanax, Giant
Nuckelavee
Ozaena
Scylla
Sea-Mare
Shiressa
Stonefish, Giant