Jumping off a bridge at night, using a tire as a flotation device

It was a couple friends and I, and we were on some bridge after nightfall. Laughing hysterically and trying to avoid something that must have been to our back, we took the leap off of this old, wooden, rusty bridge. Must have been twenty-five, maybe thirty feet tall. One of my friends was using what appeared to be a life preserver of the ring variety, complete with rope and the red "+" on the side. I apparently found a tire for use of the same purpose, and the third in our group simply swam to shore. WTF #1- Once on land, the once very official-looking life ring in which one friend had used for safety, had now taken the image of a small inflatable beach ball. The rest is considerably blurry. I recall being at a house, with both friends and one's girlfriend. Drinking, laughing, and surrounded by both familiar and unfamiliar faces, it was a great time. Someone needed a ride and asked a friend of mine to oblige, which they did and I went along. WTF #2- What must have been a local, unmarked cop pulls them over. However, I'm in the passenger seat of the cruiser, and vaguely recall stating, "yeah.. that's them. We got 'em."

Seven hours after waking up, this is all I can gather. Any thoughts, opinions, or theories on this?