Indeed, this is kind of like the Sesame Street game of "Which thing doesn't belong?" And you're right to say it's the swimming pool that doesn't belong, because the swimming pool is the only thing on this slide that's actually very dangerous.
사실, 이건 세서미 스트릿에 나오는 "어느것이 외톨이인가?" 같은 게임이에요. 여기서 외톨이가 수영장이라고 생각하신다면 제대로 보신겁니다. 왜냐하면 수영장이야말로 사실은 굉장하게 위험한 곳이거든요.