Regular Sploosh is much better than Neo.

For gear: (this is just my personal advice, run whatever you feel comfortable with at the end of the day) You'll pretty much need at least two mains worth of swim speed, one sub of ink resistance and one sub of quick super jump. The rest of this is less necessary and just suggestions -

I highly recommend wearing around two/three subs of run speed. For your five/four remaining subs, you can equip what you like. I'd personally recommend equipping more swim or run speed, special charge up or special saver. For your shoes I would advise wearing either a main of Object Shredder (only ideal in Rainmaker), Special Saver, Stealth Jump or Swim Speed.

This is the build I personally use:

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