Yari Spear is nice, and maybe an Indian Kukri Knife with fish tail scabbard as the secondary weapon? Or a Kukri Sword as the main weapon. The reason I like this weapon is that it resembles a fin as well as having similarities to a wave, tide or flowing water.
I kind of like the idea of her being able to throw globes of water. Maybe they kind of maintain their form could drown someone if they hit their head, or weigh down an appendage if they hit a hand, etc. Or even as distractions they might be useful. Can call forth steam, perhaps? Combined with a spear of some sort. A few of the other girls have magical powers, so I figure it's not too crazy. Or perhaps she can become incorporeal by turning her body to water (but still maintaining a human shape) or a mist? Maybe she can 'dessicate' her enemies by sucking water out, either with a magic spear or via touch? Or create healing waters she and others could use. Anyway, hope you got your answer!
