Watch the Night Gallery episode featuring, “Lindemann’s Catch,” for a different kind of mermaid tail.
Ask any mermaid you happen to see,
“What’s the best tuna?” “Chicken of the Sea!” 
The Little Mermaid’s little sister
was also partly girl and cod,
though in a way that those who kissed her
found odd.…but which, well worth to mention,
though at first sight absurd,
I, with my fond intention,
preferred.
— Piet Hein
Or you could just have a look at Sarah Hingley’s “Fishbutt Fandango”:
https://www.etsy.com/ca/listing/680453811/fishbutt-reverse-mermaid-fishbutt
Also Mulan, Rapunzel, Merida (Her mother was a major character even), Tiana, and Moana. Six out of 13 official.
Right, that gives some drama.
Nope.
Tinkerbell, Alice, Esmerelda, and Jane Porter were once, but no longer.
Of the 13, Mulan is the only one who was never a princess by rank- but is Official. Her father was a noble of some sort and she married a General.
Elsa spends most of Frozen and all of Frozen II as a queen.