I just randomly stumbled upon a performance bug which would make the game drop dramatically in framerate.

Go to a place with a bunch of water, like the water near Crazy Joe, or the water in The Well in Wellspring - stand right in it, crouch and look down on the water.
You should see a blob of white water appear, and suddenly the performance will be really bad, but only while you look right into it.

Tested to be in effect on both my desktop, laptop and also the Xbox 360.



I suppose it's related to overdrawing when the transparent water splash textures stack up on top of eachother like that.

Yup, seen this one too. I think it's more a case of a fairly complex shader having to run on every pixel in the framebuffer than it is a bug though.