For the last hundred years or so, people have claimed to have seen a monster in the Scottish lake
Some people think that Nessie could be a plesiosaur, a massive creature thought to have gone extinct with the dinosaurs. There are theories that there could be a big underwater cavern where a few of them hid when everything else died, and they've lived there to this day.
Sometimes sticks look like monsters! Sometimes it's hard to tell how big something is. Something that's small and nearby ends up looking like something big and far away!
Monsters are fun, so it's not out of the question that people sometimes just pretend they've seen one
There's one theory that the Loch Ness Monster is actually a Greenland shark. It's a shame it's not a long-thought-extinct creature, but SHARKS ARE GREAT!