I think it might be during the 4th of July on 2017, when I went to my friend’s vacation home. There was a pool, there, and in the pool was a huge inflatable that was something like 4 floaty seats with a cooler in the middle. I tried swimming under it to see what it looks like from below, and surely enough, it started following me as I tried swimming back up to the surface. I thought I was gonna drown, but somehow, I managed to resurface.