D&D General Suggest to me a dangerous sea monster from any edition

[Sword of Spirit]

I have a specific scenario that's coming up soon in my campaign, and I need to pick a monster from D&D's lore. It's a 5e (2014) game, but I can convert the monster myself if it doesn't exist in 5e. Our lore favors 2e, which has a zillion monsters, but I couldn't find exactly what I'm looking for from a real quick search. Here's the scenario.

Through very powerful magic, an NPC is going to conjure up a massive storm at sea, and a terrible monster is going to arise from the depths, and threaten a ship that the PCs are captaining.

Desired results:
-The monster is escapable (and will not pursue)
-The monster will do some damage to the ship before being escaped (could be a risk of destruction, or just a bit of damage before they escape)
-The 5th-level characters can survive a round or two of combat
-Does not create a massive wave that damages everyone on the ship, since some NPCs should survive (see below)
-The monster isn't something you can negotiate with, and makes sense being summoned by the spell
-The monster will hang around for a week or two along with the storm it's summoned in, to deter going back that direction
-CR probably mid to upper teens, should be something the party knows is beyond them rather than something they think they can take on

I looked at the monsters that already exist in 5e that might fulfill the roles, and am not truly happy with any of them. A dragon turtle shouldn't really be summoned from the depths. A typical sea serpent might be, if I want to create a more powerful version. Giants and such are too easy to negotiate with. A kraken seems too dangerous, and I'm still not sure the "young kraken" idea works for the kraken lore I'm leaning towards. The 2e (whale) leviathan is a good guy that shouldn't behave in this manner.

The best I came up with so far is the 5e (elder elemental) leviathan. It seemed like a pretty good fit, except for its tidal wave ability (I like the 2014 better than 2024). The only way I can make it not too deadly (especially to the NPC crew) is to have it start the wave conveniently a round or two behind the ship, so the ship can just continue away from it (this ship is particularly fast, and with the same speed as the wave it should be able to stay above it). But the whole way I have to handle it is too complicated and contrived, and if it doesn't go right everyone dies, which isn't how I want it to go down. I'd rather the PCs have more than exactly one way to get themselves, the relevant NPCs, and at least some of the crew to safety.

So, what dread sea monster that would make sense with these parameters can you think of from any edition of D&D?

 

[Plaguescarred]

A Zarathan could be an option and if too powerful, make it juvenile perhaps.

 

[Muso]

Dragon turtle?

 

[sevenbastard]

Invisible Stalker....wait thats a cant "see" monster.

 

[Alzrius]

When in doubt, look to the classics; I'd recommend a scylla.

 

[Sorinth]

A storm elemental could work. Lightning attacks can target players but not NPCs as well as damaging the ship without sinking it by targetting the mast(s). And having it well above the ship using ranged attacks make it less likely the PCs try to really take it on.

 

[aco175]

Kraken. Lives in the deep and comes up to hunt every so many years when disturbed like a dragon. There was an adventure where the tentacles acted like individual threats and you could affect different things from being destroyed on the ship. Each tentacle could also be a decent threat to 5th level. Kill a couple of them and the thing pulls back for a few rounds allowing the ship to flee.

 

[MechaTarrasque]

Sea Linnorm was my favorite 2e sea monster.

 

[Brendan Byrd]

3e - Dire Shark(s)

 

[Tonguez]

What about the 2e Tempest ie The Living Storm Cloud https://adnd2e.fandom.com/wiki/Tempest_(Creature)

or the Maw of Sekola

or maybe Scylla (posted above)

or a Riptide Horror which we created right here at Enworld