Underwater Dungeon

[Celcey]

Greetings Playgrounders! I am about to run an underwater dungeon for my players and I was wondering if you guys had any ideas for how to make it more interesting. Particularly good RP encounters with Merfolk, interesting traps or puzzles or other such things, or interesting under water battles. They're a party of three at level six, so homebrew monsters are welcome if you have any- the Monster Manual is severely lacking in underwater creatures for their level range. They will have waterbreathing and a swim speed via borrowed magic items (a temple is lending it to them in return for beating the monster).

[Mutazoia]

Hunt down a copy of "Stormwrack". It's 3.5, but there is a lot of good info, and there are a few forums talking about how to modify it for 5e.

Traditional traps are not really going to work under water, so you will probably have to make good use of currents and tides. They could be swimming along and suddenly get hit by a very strong current flowing down a cross passage, that sweeps them away (doing damage as they bounce off walls) into another part of the dungeon.

Along that line, whirlpools are fun as well. Especially if they are pulling everything down into a serrated chute....

AOE electrical traps are fun under water. A good lightning bolt turns into a fireball under water.

Strangling sea weed, and hallways full of jellyfish...

[JellyPooga]

Don't forget that Undead, Constructs and various other creatures do not breathe (as opposed to being able to breathe underwater) and as such are viable encounters in an aquatic adventure.

[Cespenar]

Have a crafty merfolk assassin steal one of their water-breathing magical item and try to escape with it.

Have them wander into a (small) dead magic zone that renders their water-breathing magical items unusable.

In other words, have them appreciate the luxury of breathing underwater.

[bc56]

If you're looking for good ideas for underwater dungeon design, I suggest looking at gameplay footage from the video game Subnautica. It's a sci-fi exploration game, but it's all underwater, and there are some interesting areas which are essentially dungeons. Specifically, look up these:

Subnautica Aurora
Subnautica Second Degasi Base
Subnautica Third Degasi Base
Subnautica Disease Research Facility


Having dungeons that are partially flooded is pretty fun, especially with a low-level party that can't use Water Breathing. I ran this one for a second-level party once.

https://strolen.com/viewing/Sanctum_of_Water


Another idea would be to have a dungeon that was once above water, but is now beneath. That way, you can come up with interesting ways that normal traps become more effective, thanks to malfunctions due to being submerged.

[Corsair14]

Also remember sound travels very well underwater and any large boom could be deafening. Any vigorous movement will stir up dirt and debris on the bottom making it hard to see for large periods of time and possibly hard to breath.

[Ninja_Prawn]

homebrew monsters are welcome if you have any.

Ooh, I have some of those!

Unfortunately, most of them are currently available to patrons (https://www.patreon.com/posts/high-seas-update-15895685) only (though it's only $1 for access if you were interested).

However, I can give you a taster! The 'high seas' tag (https://nailsofvecna.tumblr.com/tagged/high-seas) on my Tumblr has a few monsters (the skeleton crewman might be of particular interest) and I have a whole raft (http://mfov.magehandpress.com/2017/07/familiars-under-sea.html) of tiny aquatic CR0s (i.e. things that would be good familiars for this game). I'll also give you these merfolk, which haven't been freely published anywhere else:

http://i65.tinypic.com/2hzl575.png
http://i67.tinypic.com/2cmrmh2.png
http://i65.tinypic.com/qntw0l.png