Underwater vessels for campaign

[FrancisBean]

Has anybody done any design work for underwater, submersible vessels for a campaign world? I've got one where those things might exist, and I'm looking for ideas. I might even retcon some into my world. My party is mostly air-breathing, so this is largely for fluff and flavor, but might matter when they get to the point that breathing water is an option.

I'm got two specific cultural examples, although others are welcome.

First, and most obvious, the Sahuagin might have submarines -- really just underwater chariots -- drawn by megalodons (Giant Sharks, MM238).

Second, the Sea Elves (with a large presence in my campaign world) would have similar vessels drawn by Narwhals, the Unicorns of the Sea.

I've got nothing in mind for the merfolk and tritons, but it makes sense that they'd have something. The Kuo-toa seem too disorganized to have anything of the sort, but I'm open to ideas.

The tactical analysis between the two types I listed is very engaging. The SharkShips can descend much farther, because they never need to come up for air. They're also very dangerous in tight quarters with no room to build up speed. The Narwhal ships can do impressive nova damage, even to a structure, if they have room to build up speed, but they need to stay close enough to the surface to breath every 90-210 minutes.

There's nothing here I need anytime soon, but it's an interesting idea I wanted to toss out. Maybe somebody has already done work on this. Maybe I'll spark some ideas! I've never seen a D&D game set in submarine battle, and this would be a unique way to try it out.

[Falconcry]

(5e) Acquisitions Inc Has that beholder mech that you could retrofit as a diving bell for you party. There is also the apparatus of the Crab.

[Khrysaes]

Old materials, but they can give you Ideas.

Gnome Submersible
Arms & Equipment Guide (page.53)

Undersea Ship
Exploring Eberron Pg 40

From 4e
'Sea Reavers of the Shrouded Crags' in Dungeon 158 involves a dwarven submarine.

Manta of Sauhuagin
https://forgottenrealms.fandom.com/wiki/Manta

Apparatus of Gond from the video game Neverwinter: https://neverwinter.fandom.com/wiki/Apparatus_of_Gond

Then for 5e there is
Scarlet Marpenoth from chapter 7 of Waterdeep Dragonheist.

Apparatus of Kawalish
Dungeon Master's Guide , pg. 151


Also, Makes me think of Disney's Atlantis and Justice League: Throne of Atlantis when Ocean Master attacks Metropolis

Final edit:
https://www.dmsguild.com/product/368...ater-Campaigns

And you may get some ideas from the Spelljammer ships

[Nidgit]

I've got a hook coming up where a Githyanki creche has been cut off from the Astral Plane so they've adapted one of their ships into a sub for some coastal raiding.