Searching a river for a weapon used in a crime. The side we started on was very silty and had lots of fallen trees and limbs (very difficult search for a relatively small object). After our first dive we were discussing among the divers our "confidence" level that the area could be considered clear (it wasn't great), the deputies overheard us and were pretty upset that THEY were wasting their time. As we walk back up the trail to exchange tanks we heard some commotion and a gunshot. Upon our return with fresh tanks, they happily informed us that it wasn't a complete waste of time because they got some target practice at a snake swimming down the river.
..Seriously?
Next dive I hit the channel and it turns into a fairly nice pebble and slate bottom with relatively fantastic vis. We get done searching, and one of the deputies makes a smart remark once again about wasting his time. I reach in my BC pocket and throw the freshly shot bullet he fired at the snake in his lap.
It was glorious.
Get back in the truck, my buddy stares a hole through me and asks, how in the world I found that. I told him it was sitting on a large smooth piece of slate, glistening like a flare in the sunlight. Apparently his second dive missed the channel.
Definitely not the most unusual or coolest thing I've ever found, but I enjoy thinking back about it every time people ask me a question like this.