Laura Thorn's oxygen tank

"Ah, that looks like a Muggle 'fire distinguisher'!… But there wouldn't be many fires on a lake, surely? What? Oh, right. It's an oxygen tank. Of course. So Laura was diving in the lake! If only we could've stopped her… But look at these dents in the metal! Myra has to see this; it might tell us how our intrepid monster hunter came to be injured!"

- Mathilda Grimblehawk and her partner collect Laura Thorn's oxygen tank

Laura Thorn had an oxygen tank, which she used for underwater exploration, in her quest to find magical creatures.

Using this oxygen tank, Laura Thorn ventured into a lake in which there was a particularly vicious Grindylow. When she was attacked by the creature, who tried to throttle her with its long thin fingers, the oxygen tank was badly dented when the creature repeatedly hit it with its small horns. The oxygen tank was later retrieved by Ministry investigators Mathilda Grimblehawk and her partner, who, together with Myra Curio of the Muggle Liaison Office, used the pattern of the dents on the oxygen tank to determine what kind of beast had attacked Laura Thorn.