I really like this setting.
I am having a little difficulty understanding the water levels however, particularly the relationship between the shaded areas and the dotted lines. I've been guessing that the shaded areas represent caverns that are always flooded (per the title) and the dotted lines represent high and low tide. If that is the case, I'm not getting the dotted lines in the lower left chamber as well as around the pool in the lower right. Any insight would be appreciated. Thanks.
So, the fully gray chamber in the lower left is because I screwed up my inking. The gray represents lower level chambers that are fully flooded, while the non-gray chambers are surface water with air above. The dotted lines represent openings that pass between the upper and the lower chambers. If I were making the map outside of the map-a-day schedule I set for April, I would have added an elevation view to clarify.