If you ask anyone with a background in chemistry, they’ll tell you that sulfuric acid is a pretty nasty substance. Not only does it give off a potent smell, but it can also be deadly to humans in surprisingly small quantities. That’s why it’s totally insane that adventurer George Kourounis decided to take an inflatable raft into the acid lake inside of Indonesia’s Kawah Ijen crater.

The lake is full of sulfuric acid that’s strong enough to eat through metal. Kourounis can thank his rubber raft for keeping him afloatĀ since the material stands up well to the corrosive substance over short periods of time.

That being said, it’s still pretty nerve-wracking to watch.