The dark (working on it, I am not as scared of it as I used to be).
Seaweed.
Spiders, insects, crabs, (you get the idea) especially large or unusual ones.
Deep water (my imagination assaults my rationality with sea monsters to startling effectiveness).
My French teacher.Most of all... RUBBISHY THINGS!! !
stuff like receipts, bits of paper (especially wet ones), tickets, dirty dishes, yoghurt pot lids, small plastic bags, the list goes on...
Even worse if they are wet. Seeing people lick the yoghurt pot lids makes me want to sick up and I shudder uncontrollably.