Jungle Beach used to be quite isolated. You'd need to go up the Peace Pagoda, well off the main strip, and then hike in a circle round a peninsula before you arrived. Now you still need to get to the Peace Pagoda but they've cut some stairs straight down the hill and once you get there there are beach beds and a little restaurant. We're not sure if this is necessarily a good thing, but it does make access easier.
The beach is nice, it's swimmable, not rough and just the right size. When there are too many people, however, it becomes like any other crowded beach, AKA, not cool. Jungle Beach is still far enough from the main strip that not sooo many people come.
Jungle Beach is a swimmable, isolated beach
If you want to visit the Peace Pagoda, bring a sarong to cover your legs.
https://www.yamu.lk/place/jungle-beach-unawatuna/review-23718#full