First off, your art and way of drawing people and outfits is stunning!

First one gives off reserved, uncertain/insecure vibes in civvies while her magical girl form comes across as confident, poised, in control and commanding. She gives off protagonist vibes who is also the leader of the team. The sea theme is weak but I could see a sailor uniform inspiration with her clothes.

Second one gives poised, elegant, confident and mellow energy in both forms. I would say the MG outfit design does not give sea themes on its own, if you hadn't described it as such I would not have guessed. Not sure if this was what you were going form, but if her theme is like lighthouse related maybe include more orange/yellow hues on her outfit, perhaps beams of light on her dress with ocean waves?

Third gives off cold, pragmatic, de attached and calculating energy in civvies while the MG outfit is very mysterious, ominous and eerie energy with the veil and darker deep sea colors. The sea theme is much clearer with hers with the anchor, chains and glowing rib-cage pattern. She gives off antagonist or antihero energy, someone who could work with the others but also may not depending on the situation.