I don’t really have any requirements. I think it would go well with the Sea Elf Outpost in the vicinity, but I haven’t really thought it through. Tropical? Or maybe a little outside of that? Not really sure. No specific requirements.

Thank you! I definitely plan to submit this one to the Atlas. Nothing would please me more than to get a message from a stranger saying they used it in their campaign, and all of the antics that ensued.

Here's what I've done with adding murkiness to the heart of the Sea Hag's lair, and softening the cliff edges with weeds and rocks and weedy rocks. Oh, and a pile of bones and other debris.

Okay, I've had a chance to do some experimenting.

@Don Anderson Jr. -- here's a test putting things on the SYMBOLS WALLS MARINE sheet. #A is from the Weeds symbols, #B is Seagrass, C is coral, D is the Wall Weeds, and E is Weedy Rocks. What do people think? Any favorite combinations here?

@Wyvern -- I experimented with creating a murkiness by adding the ADJUST HUE/SATURATION effect to the DEEP WATER sheet (which I moved above the walls so that the walls would block it), and then lowering the Hue and increasing the Brightness. I then used the "Water, default, deepest" for the areas closest to the Sea Hag and the "Water, default, deeper" for the murky water farther away.

Honestly turned out better than I expected. I created a DEEP WATER 2 sheet so that I could have different settings for the Deeper and Deepest water. Doing it this way allows me to keep the rest of the ocean untainted. Now I have to decide how pervasive the murkiness is. I could make the entire head area the murkiest, with the less murky fill permeating the rest of the lair, or maybe most of the rest of the lair. Or I could keep the murkiness just in the head area.

I will also add some bones and other debris, though probably won't add too much clutter.

Very Cool! I will experiment with vegetation and maybe saturation/brightness, or maybe shadows, though I want to make sure I don’t lose the beauty of the Marine Dungeons.

I'd like to be

Under the sea...

Here is the second of the three Marine Dungeons I've planned. The first was the Sea Elves Outpost, and the third will be a full-scale, multi-story underwater fortress (though it may take me a bit to get to it, as I'm letting myself get sidetracked).

My goal with this one was to go for speed. I wanted to see if I could create a nice dungeon in a reasonably quick amount of time. Like, imagine it's a Friday evening and I have to whip something together for my players who will be coming over Saturday morning.

I have a collection of public domain images produced by the Society for Creative Anachronism for use as heraldry symbols, and I used one of an octopus to use as a tracing guide. All told, it took me about four hours, I think, to do the first draft. I then went back to rip out the gardens that require sunlight (per the conversation in the Sea Elves Outpost thread) and replace with things that wouldn't require sunlight.

This one is called The Octopus' Garden. It's unknown who first excavated this realm beneath a marine mountain, carving it out in the shape of an octopus, but it has now become the lair of a Sea Hag.

Here it is unlabeled:

Here it is with labels:

The octopus' eight arms serve as wings in the lair (or maybe we should say tentacles instead of wings), with the suckers becoming small rooms in the lair. The southernmost tentacles open to the sea, becoming entrances to the lair, while the other six are fully enclosed. The chambers in tentacles 1, 2, 3, and 4 are used to produce food for the lair's residents.

As you enter -- if you can get past the sharks that the Sea Hag has enchanted to guard her entrance -- you'll see that the chambers closest to the entrance get just enough sunlight (improbably) to grow vegetation. The other chambers grow things that don't need sunlight, particularly marine mushrooms. (True story: freshwater aquatic mushrooms were discovered about 15 years ago. They're only found in a single mile-long stretch of the Rogue River in Oregon, in a spot where my family has a cabin that has been in the family for generations. But in my fantasy realm, saltwater mushrooms are abundant.)

Other chambers are used to raise shellfish, sea urchins, and anemones, who are all fed with vegetation harvested from the kelp forest outside of the lair on the northeastern side.

The chambers in tentacles 5 and 6 are all prison cells. If you look closely, you'll see a double set of gates in the entrances to those chambers. They all have hammocks for the prisoners to sleep in, but they are also all equipped with shackles bolted to the lair's walls for situations where a prisoner may need extra restraints. If you look closely, you'll see that two of the cells have humanoid creatures (probably sea elves) shackled to the walls. Another has a humanoid skeleton, while a fourth has the skeletal remains of some other creature. A fifth has an imprisoned mermaid, and the others in this closeup are unoccupied.

The chambers in tentacles 7 and 8 are are bedchambers, each equipped with a hammock and one or more chests so the resident's valuables don't go floating away.

The "head" of the octopus is a Great Hall, where the Sea Hag holds court. Today she has chosen to take the form of a giant octopus.

The two spots labeled #10, where the octopus' eyes would be, are extraplanar portals. Some say that one goes to a dangerous swamp in the Feywild while the other goes to an even more dangerous fen in the Shadowfell. Others say they go to the Elemental Plane of Water, or to soggy planes of the Abyss.

Why would our adventurers go there? Perhaps they are trying to rescue the mermaid, or the other NPCs. Perhaps they need to use the portals to get to the next stop of their missions. Perhaps they need to negotiate with the Sea Hag for help with something. (Maybe one wants to trade her voice for a love potion -- no, not that.) Maybe the Sea Hag has a magical artifact that they need to complete their quest....