About a million years ago I used to be heavily into snorkelling, spending most days exploring the bottoms of different lakes.
Me and a couple of friends used to go night swimming at our city's municipal bath, which has a lot of swimming pools and
jump towers outdoors.
Swimming there at night is forbidden, of course, and the place is supposed to be checked regularly by security guards.
One night I went there with a friend and we spent hours playing in the swimming pools. To conserve heat the water
it is covered at night by large plastic covers similar to tarpaulins that are rolled out over the whole swimming pools.
These covers have small holes evenly distributed across the surface which can be pushed on from below the water,
creating a small area to breath from, so You can't really drown under these sheets, if you know the technique.
Anyway, my friend and I are in there when two more guys show up and begin to play rather loudly, running around
on the covers (which is fun) mucking about with a football. Now, the more noise you make the more likely it is it will
attract the security guards who sometimes pass the place in their patrol cars. It would be nice it they could just leave.
After about 20 minutes they sit down on the cover, in the middle of the pool, hanging their legs into the absolutely
ink black water, chatting.
This is in the middle of the 50 meter pool, where there's a half meter gap in between the two covers on that pool.
It's night, pretty dark and these guys haven't seen anyone there... I take a deep breath, swim about 20 meters
under the cover, slows down close to them and suddenly clamp down as hard as I can with both my hands on
one guys calf, just above the foot.
Then I begin to drag him, and the cover, backwards over the pool. I had divers fins on my feet, which made me
super strong underwater. I didn't want to drag him down into the water, so I made my pull horizontally.
After maybe 10 seconds I released his foot and slowly swam back to my friend who was by the edge of the pool.
When we looked over the cover we could see two guys hysterically running towards the horizon, a couple of
hundred meters away.
It is unknown if any of them ever took a bath or a swim again...