Dead Man's Mouth is a location on the outskirts of Beach City.
Dead Man's Mouth is a small lake surrounded on three sides by small cliffs. There is only one opening leading to the lake, and it is marked by enormous boulders near its entrance. The lake itself is simply a small body of water with rocks strewn across it.
Dead Man's Mouth is a popular place with the youth of Beach City but left alone the majority of the time. Following the time after Rose Quartz gave up her physical form, the Magic Moss she tended worked its way into the lake and festered there for an indeterminate amount of time. Dead Man's Mouth is now clear of moss and is assumed to be safe for humans.
The Crystal Gems realized the danger the magic moss could present to humans and Pearl quarantined the area off with some police tape she had stored in her gemstone. Despite their best efforts the rebellious "Cool Kids" decided to hang out at the lake. When they came into contact with it, the moss seemingly became aggressive. It engulfed Jenny, Sour Cream, and Buck Dewey until Lars and Steven managed to pull it out of the lake and drive it out of Dead Man's Mouth. It then transformed into blossoms on a hill nearby.
- The first part of the name is a popular naming convention for dangerous roads or locations with a notorious history, such as a Dead Man's Curve.