It lived in the water and belonged to the group euripterid, they were a group of arthropods that resembled scorpions but were more closely related to horse shoe crabs.
It was a large creature that ate anything it could grab with it's claws but was the size of a panda, or a go cart.
At the time more than 300 million years ago, there was a lot more oxygen in the air so creatures could grow a lot bigger and still move quite fast.