At my D&D game this week, we were playing a sci-fi horror game. The submarine had been infested by some sort of alien slugs. The slugs would burrow into a body, then a huge boil would appear, with more slugs squirming and moving under the surface. Eventually, this would burst open, making the situation even worse.
We found this out when we found the chief engineer's body in the ballast tanks. We pulled him out, and one of the other players said that she would watch the boil closely in case anything happened.