Rylands vs Fletcher - What's the Logic Here?

Guys, I'm so lost. I've been trying to wrap my head around Section 7 of the Torts Act (not IPC, okay!) and I just can't seem to get it. So basically, it says that a person who brings onto their land any things or animals is strictly liable for any damage caused if they escape. But then there's this thing about 'non-natural use of land'. What's that even supposed to mean? Is it like, if you have a swimming pool in your backyard, you're not liable if someone jumps in and gets hurt? I mean, that sounds more like a negligence case to me. And then you have this judgment where the court says that a reservoir is an 'inherently dangerous' thing, but what about all the dams in India? So, what's the real rule here? I've read the notes, but it's just not clicking.