[antipaganda]

There is a HUGE flaw in your analogy here: "If people did go in there and got killed we'd cover the event in detail on TV, as a warning to others (like Shark Week). Even really stupid people would know not to go into the "valley of the stabby monsters."

Dolphins don't have TV. They have no technology, apart from using sponges to protect their noses.

Imagine that, back before the Stone Age, you were a primitive hunter-gatherer, and you had to warn the entire world population about the valley of stabby invincible guys, since you were the only survivor of the last massacre there. How the hell would you do it? Who would even believe you?