Holes (trypophobia) and sharks in the pool. I used to be on the swim team and loved swimming, but at some point in my teenage years I got this irrational fear that a shark was chasing me in the pool and now I literally can't do laps anymore. It sucks cause I really enjoyed it and I was good at it. Nothing triggered the fear as far as I can remember.
The trypophobia I have many theories but I think it is actually just one of those fears people have sometimes.
Edit: I clicked it actually, you got me. It is not a holes trigger so it was ok. Actually looks like a pretty amazingly awful movie and I may just have to watch it.