Whenever I see or even hear of a gory and violent death that happens underwater, I feel disturbed by it for days. For example, I even cringed when I heard about that acid scene from the film Untraceable when I never even watched it. I get afraid when I see sharks feeding underwater. But when I see them on dry land I feel less disturbed. I even watched tons of incredibly gory shows and they didn't really disturb me. But when I think of graphic deaths underwater it really disturbs me. Is this normal?

"sharks are scary when they're feeding underwater but not scary on land"
No kidding.
Is it something that could give one, nightmares? Or is it worse than anything I could ever imagine?
It was reasonably common for men to fall into them and they died by simultaneously being:
(a) drowned in concrete
(b) threshed by blades chopping through their body and limbs
(c) crushed between rollers
I just didn't like it. :/