I inherited a pond and have waterfall feature.

It hasn't been working for a while as I only got round to replacing the pump.

Now it does work but there is a leak coming down to the outside of the wall and also to the bottom of the rocks. I think when it leaks to the bottom of the rocks it seaps into the wall (I hope you can see from the pics)

I'm not great at DIY so don't really want to take the cemented rocks off and was wondering if cementing over the leak on the outside wall or using sealant on the outside would be a solution.

The water is leaking on the create or slabs so not sure that will cause a long term issue?

Thanks in advance for any advice