Spa leaking under spillway

[Ballcaddy]

It appears water is leaking from inside the spa thru the mortar, between the spa waterfall stone and plaster. Water is dripping out underneath the spa ledge into the pool. The leaking will stop once the water line reaches the plaster. I want to seal the mortar and what would be the best product to stop the leak? Would a polyurethane sealant work or would I need more of concrete type product?
Thanks

 

[markayash]

Maybe use jbweld waterweld? Its a putty and you mix it and shape then let it dry. Its water proof.
I have a similar issues years ago and not many products hold up when under water all the time even though it said waterproof