Water Weird Ruins

From publisher blurb: Water Weird Ruins is a Fifth Edition plug-in adventure for four characters with an average party level (APL) of 8, 11, 14, or 17. This addon offers details for each level and makes adjustments accordingly. Deadly elementals, both living and undead, haunt the crumbling ruins of a flying castle. Characters exploring the ruins discover clues pointing towards vast wealth hidden in the ruins’ numerous secret areas.