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.
实际上，这就好像“芝麻街” 游戏中的这个问题： “以下哪个选项与其他不同？” 理所应当你会觉得 游泳池跟其它的都不一样， 因为游泳池 其实是最最危险的场所！