Massive FPS dropps!

[Batar]

Hay!

Aight,so when i normally play i don't have any problems at all with my FPS,but when i am somwhere it's like on the picture my FPS dropps from a steady 60 to like 10-15. Only when i look straight in to it / or covers a big part of my screen and it doesn't have to be just water,but any "massive" amount of details like that. I've been trying to sort out the settings but i can't find the one that would help. So,any of you know which setting i should "turn it down" on?
Appreciate your help!

http://imgur.com/a/oCkWF

[Rawwrz]

This started happening to me awhile back. Anything like that water or that new fog effect they use in a few instances/raids really hammered my FPS. I lowered particle density and it helped a tiny bit. So I just took everything else down a notch and it seemed a tad better. Even so I still see a drop in that new fog affect like in Darkheart.

I'd start with particle density and see if that helps. If not try what I did knocking everything else down a bit.