Need to resurface a rock waterfall?

[WillDeed]

My rock waterfall is leaking in the back, so I thought it might be time to resurface it while also repairing the leak. I bought Pond and Stone insulating foam for the leak, but I have no idea what was used to cover the rocks (or even if the rocks are supposed to be completely covered versus just in the crevices between)

In the attached picture, there is a blacker "mortar" between the rocks. I assume it used to completely cover the rocks, but maybe it's supposed to just be in the cracks?

I inherited the pool, so I don't know what it looked like new.

Any thoughts/suggestions? Does it need resurfacing or is that not a thing? Is the black stuff just insulation foam?

 

[ajw22]

Are those natural rocks or faux rocks?

Why do you want to resurface natural rocks?

 

[WillDeed]

I don't necessarily want to resurface it. It looks like it is in need of some sort of maintenance to me, because that black mortar-like substance seems to be eroding. But I don't know what it is supposed to look like, so maybe it's fine the way it is.

That's really the heart of my question - is there some sort of maintenance I should be doing on the rock feature or just plug it when it leaks and call it good?

I assume they are faux rocks, but I also don't know how to tell the difference from natural rocks.

 

[ajw22]

Plug the leaks.

Any maintenance you try and do will just cause more maintenance requirements in the future.