I've done this loads of times and the results are good people always ask what did I do, Paint it, yours sounds pretty bad I think first you would have to get some cement and fill all the cracks and holes,
Here's what do, clean it first get rid of the black algae then get some primer don't forget the primer maybe give it a couple of coats, then paint it with any colour you want make sure you buy something like Dulux weather shield it has a fungicide in it so that will stop any mold forming,
The last one I did was around a pool the colour I used was Brilliant White also painting last longer than cleaning the sandwash.