Your prediction is not entirely wrong, at least it wasn't for Localbitcoins a couple of years ago. Check this thread.

As you can see, that guy could make profit due to the fact that prices on Localbitcoins are less competitive than on a large regular exchange, such as Coinbase, which is probably explained by the comparative maturity of both platforms. Localbitcoins has grown pretty well since then, but Waterhole is still young, as you've said it yourself, so you can go ahead and try making money there.

However, be advised that there are also some risks, which are too covered in that thread.