Finally got Illustrious version released. Use that or Pony V2 for best results.

Main appearance tags: mermaid, mermaid tail, head fins, green hair, purple eyes, purple tail, ahoge, side bangs, hair over breasts, large breasts

Clothing tags: black t-shirt, red skirt, pleated skirt, shell necklace, bracelets, purple headband

Optional: gills, scales

Since the dataset is a little more diverse for V2 and Illustrious, you should be fine using them at 0.8 weight, but feel free to experiment. I still don't recommend you go above 0.6 on V1, however.

Note that the wan video version of the model is highly unstable and somewhat prone to deliver results that may be subpar. I advice to use it in tandem with img2video if possible in order to give it a good origin point.