Mercury Lake

A short ways away from the Cornucopia lies an underground lake; don't try to drink its contents, though, tributes, because you'll certainly regret it. From far away, the water seems to be a peculiar shade of silver; a closer look, though, will reveal that it is actually bubbling, liquid mercury. Typically no living creature would be able to make a home in this viscous liquid, but judging by the occasional fin slicing across the surface, it appears that the Gamemakers have, as usual, discovered a loophole.