Swimming lessons are only something I vaguely recall.
We had a double-PE lesson and the cold, outdoor pool was only big enough for half the pupils… so the session was split into tennis/swimming, meaning a quick change into or out of swimwear. In reality this only ever left just enough time to dip your toe in the water.
The pool had a high chain link fence around and it was not uncommon for ‘onlookers’ to intimidate the nervous body-conscious teens. Thankfully, children these days are mostly protected from the prying eyes of oddballs during school swimming lessons….