It's similar to people watching, or bird watching. The last two are things you do when you're an old gramps who doesn't know how to use internet or smart phones, & who's life is incredibly boring... But with loli watching, anyone of any age can enjoy. Some even find it more enjoyable than surfing the web. Like bird watching, cameras & binoculars are optional.
Guy 1: "Hey brah, wanna go to the local public pool to do some loli watching?"
Guy 2: "Sure bro, can't say no to the cuties!"
It's a lot like Bird Watching, or People Watching, but where you're very specifically watching loli's. Usually done in public pools, beaches, or parks.
A: Hey friend, wanna go loli watching at the local pool with me?
B: Sure! I'm sure we'll see a lot of cuties this time.