While I'm not particularly afraid of the water (or, well, if I think about how fucking deep it is, it is kinda scary, but falling off of a boat tube at about 50-70m deep didn't bother me that much), I haate the thought of being "deep" (as in 3-4m) after jumping into water, and not getting up to the surface fast enough, even though I have plenty of air. It freaks me out completely, to the extent where I'll breath out submerged and end up actually needing air before I reach the surface. Not very optimal. Also, I'm scared of sharks and snakes, but I'm not planning on coming into contact with either.
I think I also have a slight fear of heights, but mostly because I can't seem to trust railings and stuff like that. I don't understand how people can lean on railings that are more than 2m above the ground.. I keep thinking that it'll come loose, and they'll just fall down, because they've put too much of their weight on it. I think I used to do that as well, but not any more.
Oh, and fires. Ever since I was a kid, the only thing I'd have recurring nightmares about is/was fires - family/friends dying, being disfigured etc. Often there would be a fire, someone would die, it would be put out, we could all go inside again, and it would reignite, someone else would die/get injured and it continued. So yeah, fires scare the crap out of me, although not as much now as it used to.