I think both @JustinB113 and @Eleri both make good points.
@SimplyJen I spend a lot of time in Sulani. I see premades from every pack everywhere there. Kalamainu’u does have a notorious tendency to insert herself into conversations, but she never does anything mermadic or occult. I think it’s her traits that make her act the way she does.
Also, something I wanted to add to Eleri’s statement.
As I understand it, there’s a mechanic called MerWoke, that affects an entire household. Once a household is MerWoke, that’s when they start seeing merfolk swimming around with their fins. I actually think this mechanic is the reason why merfolk end up with glitched swimming. Depending on the household, merfolk are supposed to still appear human in the water… this mechanic really does not work as well as intended and that’s why I never said you won’t see merfolk swimming with a tail.
The things that can make a household MerWoke:
1. Blowing the “Ordinary” Conch Shell and asking about a sim’s strange reaction.
2. Becoming good friends with a MerSim and having them admit to what they are
3. Moving a MerWoke sim into a household
4. Having a sim inside a household become a Mer.
If you do any of these things, you’ll probably start seeing the merfolk swim like merfolk.
Sometimes… the MerWoke Mechanic doesn’t work as intended and non-MerWoke households still see merfolk in their MerForm.
Like I said… there could be some bugs or other complications with the mechanic, but I’m not an expert on programming that can confirm anything.
But, the only reason Merfolk in my save actually have a substantial mermadic presence in my save is because I use mods, cc, and cheats to increase their presence.
In all honesty, after spending years playing the Vanilla Game on the console without access to mods, I always felt like unmodded MerSims only look different from human sims. Otherwise, they act and can only really do most things human sims do. Their mermadic abilities are never used autonomously. Like, there is very little difference between a Vanilla MerSim and a Vanilla Human Sim. It’s almost strictly a difference in how they look while swimming.
Anyways, that’s just my experience with the occult.