The Red Man, or the Red Cannibal, can be spotted watching you at several locations. However, if you get too close to him, he will leave. The yacht is a common place for him to spawn, but there are many places across the island where it’s possible to spot him.
You can find a script for “Charles: The Survival Man,” which appears to be a script for a movie to be recorded in the area. Due to the year and other clues, it seems to be linked to the people on the yacht. While it’s possible it will eventually play a role in the game’s story, right now it appears to be an Easter egg. It may be a reference to the real-world TV show called Survivor.