It's funny ... normally I'm all for bikinis, but all the designs that are really catching my eye here are the one-piece suits. The Jealous Heart pattern seems very iconic of Nitrine in general, very sporty and functional. The laces on the front of the High Gear are extremely awesome. The Bubbly Sprite says to me "I am ADORABLE, dammit, and don't you forget it!"
As far as the two-piece suits, the Zesty Lime is a good, classic style, but I feel like the color clashes harshly with Nitrine's hair. It could use more of a pattern on the fabric, too, IMO. Maybe if the fabric was a deep purple and the strings were this color. I like the pattern on the Skewed Perspective as well, but I think it would work better in magenta and violet than the current shades.
I might be biased toward certain colors, though.