D&D General Whatever Happened to D&D's Sea Serpent?

Sea serpents are a staple of fantasy monsters so it's curious that they are not more prominent in Dungeons & Dragons. Research reveals the sea monster has always been in D&D, but it's taken a curious path that diverges significantly from the serpentine creature we associate with the name.

Thangorodrim
To discover the origins of the sea serpent and why its origin has been so muddled in D&D, we have to go back in time to when co-creator Gary Gygax outlined a series of GRAYTE WORMES in the postal "Diplomacy" fanzine Thangorodrim, published by the International Federation of Wargamers, Thangorodrim vol 1, no 9 (Aug, 1970), where the mottled dragon first appears:

Of doubtful species, the Mottled or Purple Worm must be included in any study despite the possibility that it is not a true dragon. The creature has no wings and no internal form or weapon unlike other dragons. Yet, its body shape conforms otherwise to the kind as does its general behavior. The Purple Dragon has a venomous sting in the tip of its tail, one drop of which is enough to fell an elephant. It is sly and treacherous. The species is found only on the Islands Umbar.

This series of dragons would become the chromatic monsters of D&D lore. Of note is that this description describes the purple worm as a dragon and that it lives on islands. That's the first hint that its origins will wildly diverge from its original conception.

Chainmail
Chainmail reiterates that dragons come in different colors, but also mentions the purple or mottled dragon, which is still flightless and has a venomous sting:

Other kinds of Dragons can be introduced into games, if a little imagination is used. White Dragons live in cold climates and breathe frost. Black Dragons are tropical and split caustic acid. The Blue variety discharges a bolt of electricity. Green Dragons waft poisonous vapors — chlorine — at their opponents. Finally, the Purple, or Mottled, Dragon is a rare, flightless worm with a venomous sting in its tail.

It's not until Original Dungeons & Dragons that the purple worm and mottled worm diverge.

Original Dungeons & Dragons
OD&D's Monsters & Treasure booklet transforms the purple worm transforms from a dragon to...well, a worm. To be fair, there is nothing in the description to indicate it is an actual worm -- it may well have been a result of artist interpretation -- but the picture makes it clear that it is an actual worm:

PURPLE WORMS: These huge and hungry monsters lurk nearly everywhere just beneath the surface of the land. Some reach a length of 50 feet and a girth of nearly 10 feet diameter. There is a poisonous sting at its tail, but its mouth is the more fearsome weapon, for it is so large as to be able to swallow up to ogre-sized opponents in one gulp. Any hit which scores over 20% of the minimum total required to hit, or 100% in any case, indicates the Purple Worm has swallowed its victim. In six turns the swallowed creature will be dead. In twelve turns it will be totally digested and irrecoverable. Purple Worms never check morale and will always attack.

Of note is the first appearance of a sea monster in the entry immediately after. That entry also makes a parallel in size and function of the sea monster to a purple worm:

SEA MONSTERS: As a general rule these creatures are more for show than anything else. However, they could guard treasure. The typical Sea Monster of mythology is equal in size to a Purple Worm, and they work upwards from there to double or treble that size. The best guide is a book on prehistoric life forms, from which the referee can pick a number of suitable forms for his Sea Monster. Typically, hits from a Sea Monster would inflict 3 or 4 dice of damage.

For one edition, sea monsters had their own entry. It wouldn't last.

Advanced Dungeons & Dragons
By the time Advanced Dungeons & Dragons debuted, two aspects were formalized that would remove the sea monster from D&D parlance. The purple worm was now undeniably a worm with no legs or anything else that could mistake it for a dragon. The sea monster was nowhere to be found, but an addendum at the end of the purple worm description provides a clue:

Mottled Worm: The mottled worm is an aquatic variety of the purple worm. It inhabits shallow bottom muck but will surface for prey. It otherwise conforms to the characteristics of the purple variety.

It seems the sea serpent, like its purple dragon cousin, was gradually changed into a mottled shadow of its original self -- from terror of the high seas to a muck-dwelling predator.

UPDATE: Updated: Pemeteron pointed out that the Cook/Marsh Expert set featured a Lesser Sea Serpent, AC9: Creature Catalogue features the Lesser and Greater versions as per Azzy, and Ralif Redhammer found a version under "Snake, Giant, Sea" in the Advanced Dungeons & Dragons Monster Manual. The sea serpent wouldn't reappear until the D&D 3.0 Fiend Folio as a Sea Drake.

 

[Tonguez]

Huh, the most interesting tidbit there is that Purple Worms werent gigantic annelids but Wyrms, associated with dragons!

Mottle Sea Wyrms are another that make more sense, And while I’d love to see a proper Sea serpent dragon, Giant Sea Snakes and Pleisiosaurs work fine as sea serpents too

 

[Whizbang Dustyboots]

Pleisiosaurs are (genuinely) great for a modern audience, which thinks of Nessie when they hear "sea monster." But they weren't what medieval cartographers or ocean voyagers were thinking of.

 

[Son of the Serpent]

I think of giants, dreki, kraken, and landmass sized individual fungi @Whizbang Dustyboots

 

[Leon Or]

In your defense, "Snake, Giant, Sea" is one tortured bit of nomenclature.

It is, however, a beautiful piece of poetry:

Snake, Giant, Sea
A sweet embrace
No breath

 

[Orius]

Monstrous Compendium Annual 2 had Dragon-kin, Sea Wyrm which is another sea serpent variant. I don't know where it was reprinted from, though.

Interesting article. I've often wondered myself why D&D seemed to lack a classic monster like the sea serpent.

 

[crystorix]

Missed that one. Sea Wyrm is reprinted from Corsairs of the Great Sea, an Al-Qadim product.

 

[David Howery]

what happened to them? The krakens ate them all. Every single one. Yep. Sad.

 

[Orius]

Missed that one. Sea Wyrm is reprinted from Corsairs of the Great Sea, an Al-Qadim product.

Huh. I still have a copy of that from when WotC had it for free on their site. Guess I didn't look at it much. Not surprising though, MCA2 had a good number of al-Qadim reprints, and a setting that was a natural home to Sinbad style adventures needed a proper sea serpent.