A polar bear at the Rotterdam Zoo in the Netherlands freaked out a bunch of tourists when it used a large rock to SMASH THE GLASS of its enclosure.

The people watching it were in a room where one whole wall is glass, so you can see the bear swimming up close. Everyone in the room immediately left, but luckily the glass didn't shatter.

If it had, thousands of gallons of water would have come rushing into the room...along with the polar bear. You can check out the footage below.

Its first attempt is at :12, but the glass cracks on the second attempt at :32.