Is it good for battles?

[Tomatoman1]

Hello.
Recently, I got a lot of water type shinies. I wanted to make a shiny water team of Milotic, Gyardos (forgot how to write it), Sharpedo, Politoed Octillery and Corphish. However Corphish isn'tisn't that great, and I dodon't want him to evolve. 
Is there a way to make Corphish usable in battle?

Thanks for helping!