Luna Lovegood and the Giant Squid
It wasn't that Luna Lovegood had forgotten the warning, nor had she chosen to forget it. It was thanks to her status as an aimless wanderer that she wasn't even present for the warning, which sadly sealed her fate.
She was wandering through the Hogwarts grounds in the middle of a very sunny day and had happened across the lake when the thought occurred to her. It was warm and the water looked gorgeous, so there was really no good reason not to go for a swim.
She undressed, already wearing a light blue bathing suit under her clothes, and slowly walked into the water. She kept going until she was up to her neck, when her body had adjusted to the temperature of the water, before she started swimming.
She enjoyed the break. Luna believed swimming to be a way of dispelling bad memories, or to simply get soaked. Her form of swimming was something of a cross between a dog paddle and a breaststroke. She was serenely happy to be all alone and surrounded by water. She was about to heavily regret