The Centers for Disease Control and Prevention has issued new guidelines on when and where to wear a face mask, which includes when diving into the deep sea.

Many people have been extra careful in wearing masks while driving, riding bikes and running alone despite not needing to, and now the CDC wants them to make sure they do the same while they’re deep-sea diving.

“If you’re diving deep in the ocean, make sure you have a mask on over your gear,” CDC Chief Robert Redfield said. “Float or swim six feet away from all creatures, even those you don’t recognize. There are a lot of monsters down there.”

The CDC has yet to issue face mask guidelines on skydiving.