Fun story - as a kid my backyard in-ground pool would occasionally get these grapefruit sized ant rafts. No idea why or how they would do it, but somehow they'd find themselves floating around in there. And if you don't look too closely it just looks like a dead leaf that landed in the pool.

Dove in one hot summer day. Came up for air. Facefull of ants. Never again.

My first thought was floating along and brushing up against it, absolutely terrifying.

middle school, 1970's NW Florida... our phys. ed. field would flood out pretty bad whenever it would rain a lot, so on those occasions we'd have a free period to just screw around and socialize. On this particular day, me, a scrawny little bug-eyed ginger kid who got picked on pretty regularly, was being chased by a group of other kids who really wanted to torture me some more. I decided to veer off through the knee-deep flooded PE grounds, which allowed me to escape my tormentors, but also gave me the opportunity to learn first hand that fire ants do indeed float in large masses, and are quite eager to swarm up on the first thing that gets within reach.

Can confirm, or if you have to walk in the water. Just one more thing to watch out for. Regular ants are bad enough, fire ants can all go to hell.

As a kid I slid down a slide once into fire ants