Fire can be great - but I went with Water because I got lucky with my Ruler of the seas. Nothing better than having it and Sea Genie against those level 3 life bots!! Water has also been pretty good for me trying to just use range attacks - without the magic boost. They seem to have one of the best low level archer decks.
Either way good luck. Let me know if you want to challenge starter deck vs starter deck!
I like the Water splinter at the lower levels too. It was the one I used to play all the time when I first started out. Back in the days (lol), medusa and the mermaid were an invincible team. I think they have made some adjustments along the way, because they are not as strong as they used to be. But the new reward cards are definitely an asset - they have made the splinter a lot stronger