Aquatic Warlock Familiars?

[Luccan]

So, Familiars and Animal Companions for underwater games are sadly lacking, but for most casters a Crab or Quipper is no worse in the water than some other options would be on land. However, the Chain Pact Warlock gets an improved companion that includes some non-standard choices. These aren't necessarily powerful, but they are different and some would argue better than the regular options. They do share the flaw of not being able to breath underwater, though. For the purposes of an Aquatic campaign I want to offer some alternative options for a chain pact warlock that will actually work underwater. So far, I have Mud Mephits (being the only Mephits with a swim speed, it just made sense to let them breath underwater). Any suggestions?

[RickAllison]

Remember that one of the Quasit's forms is a toad, so there is one existing form which you can use for aquatic scenarios. The Chwinga is another option, an elemental with some utility abilities and a swim speed.

[firelistener]

I like the octopus, personally. It's extra stealthy underwater and can hold its breath out of water for 30 minutes just in case you need it for something on land.

[Luccan]

Remember that one of the Quasit's forms is a toad, so there is one existing form which you can use for aquatic scenarios. The Chwinga is another option, an elemental with some utility abilities and a swim speed.

That's true. I'll consider the chwinga, but looking at its stat block it has quite a lot of utility compared to any other familiar (although no real combat ability).

[RickAllison]

That's true. I'll consider the chwinga, but looking at its stat block it has quite a lot of utility compared to any other familiar (although no real combat ability).

Absolutely. To be fair, the other chainlocks also are really potent. Imps are amazing, pseudodragons are less generally useful but you can milk their poison and it's kind of nice, quasits have utility but aren't quite so useful as Imp, and Sprites are the weakest but they also come with a unique ability to read alignment. And I don't mean like they show up only in a couple places, Sprites are literally the only thing that can do that. Even artifacts only have a more limited version of that, the ability to read along specific axes to accept or reject.

[Luccan]

Absolutely. To be fair, the other chainlocks also are really potent. Imps are amazing, pseudodragons are less generally useful but you can milk their poison and it's kind of nice, quasits have utility but aren't quite so useful as Imp, and Sprites are the weakest but they also come with a unique ability to read alignment. And I don't mean like they show up only in a couple places, Sprites are literally the only thing that can do that. Even artifacts only have a more limited version of that, the ability to read along specific axes to accept or reject.

Fair. Might remove Pass Without Trace (or make it self only effect, as is kind of implied) and/or Magical Gift, which are my big worries.

[RickAllison]

Fair. Might remove Pass Without Trace (or make it self only effect, as is kind of implied) and/or Magical Gift, which are my big worries.

I would agree with those changes. Pass Without Trace could actually make it more effective in-water than the true invisibility. A keen eye will see the displacement of the water around an invisible creature even more clearly than things like footprints which will likely be helped by PWT, but that +17 to stealth together with Natural Shelter means it becomes a phenomenal scout. Pack that in with its massive blindsight radius and it can spy as well. As a final bonus, the Natural Shelter leaves the Chwinga unharmed if its shelter is destroyed. If the warlock is looking through their familiar's senses, this means they know their familiar is compromised and can make it disappear before it is killed unless the enemy has specifically readied something like a follow-up attack.

[NoxMiasma]

Another option could be mephits? They are a little bigger than my default assumptions for familiar size, but a mud mephit has a swim speed at least, and a CR on par with other Chain Pact familiars. Alternatively, undead don't need to breathe ever, but they don't usually come with a swim speed.

[MrConsideration]

Could you refluff an Imp as some form of aquatic creature? Drop the Fly speed for a Swim Speed and keep other details the same.

[Meichrob7]

-Slaad Tadpole
Doesn’t have a proper swim speed but it’s a tadpole so it kinda fits. Bonus points here because Slaads have a built in method of control by stealing their gem which gives you a great reason to have it under your control.

-Oblex Spawn
Some cool imagery here with a blob moving and floating around in the water, also under the sea they’re less likely to run afoul of their weakness to fire.

-Gazer
Hover speeds are kinda different from flying speeds so I’d kinda imagine it being able to work underwater too. They also are listed as a variant familiar so that’s a plus.

-Cranium rat
Hear me out, imagine a normal cranium rat but the glass goes around it’s whole head like some glorified scuba helmet. They also light up which is nice in some of those under water ravines. It’s also got a 30ft telepathy which isn’t inherently the most useful but with 4int you could maybe teach the rat some basic language to make it a real boon.

If you’re okay with getting loose with the rules there’s some other options like the mephit you mentioned but these are the only ones I could think of besides the standard aquatic creatures that fit the requirements of cr1 or below and tiny.

[NNescio]

I like the octopus, personally. It's extra stealthy underwater and can hold its breath out of water for 30 minutes just in case you need it for something on land.

Also goes with the Ia Ia Cthulhu Fhtagn theme, for GOOlocks.