This Post is for Underwater Sea Creatures Only

As part of some other work I'm messing about with, I wanted to put together an underwater bestiary.  I don't like underwater critters in the midst of my monstrous compendiums, as they're so singular, so particular to a thoroughly separate environment, that I find I'm either using a ton of them on their own, or completely skipping over them as part of hunting for the land creature I actually want to find (and grumbling when they get in my way).  So, it made sense to me to segregate them into their own little Marianas Trench.

Below is a PDF of the major purely nautical creatures from Monster Manual, Monster Manual II, and the Fiend Folio, with errata and good art scans, saves and XP values included, and following the original Monster Manual formatting as closely as possible (with the exception of a bit of statblock rearranging).

Subentries of a major creature receive abbreviated statblocks.  Not included at all are creatures you have at least a reasonable chance of running into on land and so often appear in land-based adventures, like crocodiles, giant crabs, or giant leeches.

Full credit to Hawk for devising the clever underwater rules summary at the start, which I just ported into Word.

P.S. If anyone knows of any line art ever being made for either the Merrow or the Strangle Weed (the underwater version; I know there's art for the land version), in a module or Dragon/Dungeon/Polyhedron issue or whatever, please let me know the source.

 

DOWNLOAD

https://drive.google.com/file/d/1umbBgrQKA9X_98snAsKpYLo_F0lPcrUk/view?usp=drive_link

EDIT: Updated 20 July to v4 to add a bunch of new critters from more obscure (but still 1st edition) sources.

 

CHANGES

Beetle, Water: Changed its flight movement notation to swimming.

Eel: Reversed the XP values of the Giant and Weed eels, as they were obviously mixed up in the DMG Appendix, and then adjusted the XP of the Giant variety to match its actual Hit Dice.

Hetfish: Sourced from WG5 Mordenkainen’s Fantastic Adventure. The book omitted their movement rate; I used the 2nd edition value. 

Ixitxachitl: Added additional minor detail from Monster Cards Set 2. 

Lycanthrope, Seawolf: The seawolf entry is a bit of a mess, repeating a bunch of info as if two separate entries were glued together. I combined the two sets of info into a single overview entry, favouring specific info over general in all cases (e.g. “bites of non-fatal sort” was replaced with the note in the same entry stating that “Humans taking 50% or more damage” is what triggers the disease). 

Merman: Added additional information from Monster Cards Set 4. 

Merrow: Their swimming charge is “at 1 to hit”. I made this +1, treating it as yet another case of MMII’s issue with + symbols. Also gave them the same shaman level limits as regular ogres. 

Naga, Water: Replaced its singular composite XP value with two new values properly representing its HD range. 

Narwhal: Changed its name from the original spelling (narwhale). Replaced its singular composite XP value with three new values properly representing its HD range. 

Ray, Manta: Replaced its singular composite XP value with four new values properly representing its HD range, based on the assumption of one EAXPA (paralysis). While it has attacks that give it enough damage to technically apply another EAXPA, the tail attack is quite conditional and so I decided to ignore this special feature for XP purposes (as a lot of entries do in general).

Sahuagin: Light is stated as hindering sahuagin in the original MM entry but the precise details, though said to be later in the entry, were left out; their Monster Cards Set 1 entry adds the missing detail. Also added additional information on AC, Intelligence, and size from their DMG entry. As 2+2 HD standard examples are Medium but 3+3 HD guards are Large, and it says that certain unstated priestesses are Medium, I decided to make the weakest priestesses (3 HD) Medium in size. This is only an assumption; there is no reason that a wider range of priestesses couldn’t be Medium.

Scallion: Sourced from Dragon #89’s Creature Catalog. Corrected the Level of the young from I to II.

Seastar: Sourced from Dragon #89’s Creature Catalog.

Turtle, Giant, Sea: Assumed its original XP value (900+10/hp, a value for a 7-HD creature) was an error, considering its actual 15 HD and the fact that the very similar snapping turtle in the same entry is costed correctly.

Vurgen: Sourced from Dragon #89’s Creature Catalog.

Whale: Added information from the DMG appendix entry. Some of this information, while more specific than the rather vague MM entry, also contradicts it in spots, and still requires some interpretation besides, including carnivorous whale bite damage and every XP entry. Added additional killer whale detail (all material in the subsection) from Dragon #89’s Creature Catalog.  Fun fact: that same entry adds a 5% chance for psionic killer whales, which I excluded because there's no psionics there, but is great.