Pier Collapses and Dozens of U. of Wisconsin Students Fall Into Lake

Dozens of college kids went crashing into a lake this weekend after dozens of them crowded onto a rickety, old pier that couldn't sustain them ... and the video's absolutely insane.

The horror unfolded Monday in Madison, WI where U. of Wisconsin students descended upon Lake Mendota to celebrate Labor Day -- and where the tail end of Memorial Union Terrace pier became a gathering place for at least 30 people (if not more) ... to disastrous results.

Check out what happened in a moment's notice -- one minute, they're all there enjoying themselves and mingling among one another ... and the next, the wooden dock crumbles.

You can hear the screams both from the students who plunged into the water as well as from onlookers who saw the whole thing -- not to mention the chaos thereafter. The young people in the lake went swimming for what was left of the dock. That ... or swam for shore.

Luckily, this dock isn't too far out over the lake ... and even more fortunate is the fact that nobody appears to have been seriously harmed either. At least 25 people reportedly sustained minor injuries, and only one person was transported to the hospital for treatment.

An investigation is underway to figure out exactly what caused the collapse -- but it seems obvious ... too many bodies at one time.