Welcome to the club! Sounds really awesome how you love water types. Would there ever be a situation where you would choose a starte other than the water type?
On Topic Question:
I'd guess i'd be a swampert. My goal would be to more or less just kick back, relax and enjoy the water as a water type. I wouldnt much be into battling, although it would be a nice pass time. Really I's just enjoy the company of my water type club memebers.