A neat game!
I like the idea, it might be a good base for a great platformer game if you decide to invest more time in it. It is probably the best you could have accomplished in such a short time frame.
Some things you might consider improving:
– There's a lot of walking on dirt. I completed the game and didn't feel like there was any challenge, any real danger. The jumping was quite ordinary and enemies (just one kind of enemy) ceased to be a problem when you became able to shoot. So maybe… more enemies? More kinds of platforms? More sources of water (e.g. rain, waterfall, geyser)? Health? Whatever you want.
– The third guy is probably slow by concept and that is fine, but remember to speed him up a bit if you decide to make the levels more challenging (or it's probably going to be a bit frustrating)
– Play a sound when shooting fire?
– (Just a personal note) It's helpful for some players if you can avoid using "Z" as a control key, because in whole Central Europe (and few other countries elsewhere) "Z" is switched with "Y" on keyboards and that makes controlling the character a bit unfriendly.
– I found water that didn't kill me:
http://www.newgrounds.com/dump/item/68d78bcaebf563d16d7ddbd2d3730981
– A game-breaking bug that made me start the game over. If you step on breakable platform and let it break and reappear, it won't break for the second time (it seemed like more platforms were generated on top of each other). In this particular situation, you won't be able to proceed further:
http://www.newgrounds.com/dump/item/e22cf32674a0a094407395ee90915296
Hope that helped a bit and good luck in the competition! :)