Entomophobia. Specifically, cockroaches. We had the massive flying ones in Malaysia and I was glad when I left. A two-incher once landed on my torso while I was in the shower and, another time, a similarly-sized one landed on the nape of my neck. In a word, pandemonium.
Potamphobia/Limnophobia. Specifically, murky rivers and lakes. I won't even walk along a riverbank. I know that there's something in there that is just waiting to burst out and drag me back in. Sometimes, this fear will suddenly hit when I'm in a large swimming pool on my own and I will briefly panic. Surprisingly, I love the ocean and swimming in it doesn't bother me at all.