Extreme lag when going underwater with particles set above "minimal"

Since snapshot 14w25a I experience crippling lag when going underwater, both in Survival and Creative. As soon as I start going underwater the terminal keeps telling me that server-side chunk ticking is late by 200ms or more and it's almost impossible to do anything until I slowly get back above the sea and FPS go back to the usual 20ish.

It doesn't matter what graphical options I set, I went as low as Fast/No smooth shading/2 chunck render distance and nothing changed. Never happened before, I usually get around 20FPS at Fancy/full smooth shading/6 chunks and only a little lag when exploring new chunks, that's it.