My inspiration was that I looked at my first actual OP OC that I made when I was like twelve and said "Ew yuck" and threw her in the trash. I have a habit of making oc's for all media I like so it's more of a hobby than anything.
Judas though-, the idea that I wanted to navigate with her was that she was neutral. She doesn't play any sides and just kind of goes wherever life takes her. I wanted this un-inspired and almost sad way of living to clash with the main cast of the Straw Hats, who all have a burning dream/passion, or a goal if you will.
And then she really blooms into what I wanted her to become with Franky! It wasn't planned but it fit so well. Judas is cold and off-putting and a bit weird, kind of like a robot. The relationship she'd build with Franky would be fun because he'd sort of hold her hand and give her the tools she'd need to see what the world really has to offer. So in a way it'd be the actual robot(cyborg) showing the human how to be human! Idk I thought it was a fun idea to explore and I built from there and I've become really happy with Judas and what I've done with her. She feels organic and her relationship with Franky most of all feels organic! I have a hefty 20k fanfic sitting on the burner exploring that omg haha

About her powers-, yes! She ate the Potsu-Potsu No Mi, the devil fruit of water (bear with me) when she was a kid.
I realize it's a huge stretch that there'd be such a fruit but I mean Kuzan has ice powers and ice is essentially just... Cold water...
Judas is not immune to drowning in water though-, but she can sort of cheese her way out of doing that by pushing water away from her skin on a microscopic level-, so she's actually not IN the water.
Judas can make her body become a mass of solidifed water, so if she's shot or kicked or whatever it just passes through her. All water is at her command, rain, sea, sweat, moisture in the air and just anything that's water. Her shortcomings are that Judas can't create water, it has to come from somewhere. So if she's landlocked somewhere dry she couldn't do anything water-y.

But Judas doesn't use her powers. Other than from hiding in it and using her powers to wash her hair or something she kinda doesn't use them. She's a crazy good physical fighter and conjures canes or weapons out of solidified water to whack people in the head with.

Sorry for the long ass answer eep!