I presently have the water drained out of my underground concrete pool in Central Florida in order to replace the pool light, deal with some rust stains on the bottom of the pool and redo the planting area since we had to remove a palm tree that got too big there. While the pool is empty, I am considering the possibility of adding a return port in the side of the pool so that I could use an automatic pool cleaner. Presently, the only return is at the main drain and the skimmer. There is a raised planting area/waterfall that abuts the pool inside the pool cage (as seen in the attached picture) that would allow me to get to the backside of the pool wall without having to tunnel under the pool deck from outside the pool cage (I would have to dig straight down a ways) so that issue doesn't seem like it would be too significant. My concern is that I don't want to install another port and then have a lifetime of leaking issues. I would like to know if there is a rather foolproof way to install a PVC port under the water level that we can be pretty darn sure will not leak. If so, I would appreciate any guidance that anyone can supply as to how to best go about this.

Thanks.