I know you can swim in Hogwarts Legacy, but can you swim underwater somewhere in the game or is this not possible?
I've had friends that me that they were able to swim underwater. Is this true?
Kind of.
Hogwarts Legacy doesn't allow you to dive freely, i.e. you can't go underwater in any chosen place, even if it's a deep reservoir.
Your character can only dive near small whirlpools:
After playing the game for a few hours longer:
I finally discovered on a side quest that you can dive underwater near these small whirlpools. Inside the small whirlpools, you can search and find random loot that you can then equip or sell. In some cases, diving is also used to find quest items.