Hello pool experts!
Last year I noticed a gap forming between the mortar and rock on my waterfall spillway (see picture below). I thought it would be a good idea to inject a concrete/masonry caulk into this gap as a preventative measure.
However, I can't figure out which material to use. The area to be patched is in constant direct sunlight, so polyurethane is out (since it can't withstand UV rays). A silicone masonry caulk can withstand UV, but silicone is not recommended below the waterline. (This is the waterfall spillway, after all, so it will be covered by water 24x7.)
Then there are Polysulfide products (for boats and such). These can withstand UV rays and are fine below the waterline. However, I cannot find a polysulfide caulking rated (tested) on concrete/masonry. Any ideas?