I also have a salt water pool and five ducks we work to keep out. First off, the amount of salt we use is way less salty than the ocean or natural salt water ponds or canals where wild ducks are found. So, I do not worry about an occasional sip. Still, I don’t want to swim with duck poo so I try to scare mine out. Large beach balls floating in the pool worked well the first year I had my ducks. Sadly, they overcame their fear. They were even sneaky about it. They would peek in the windows to check that I wasn’t watching before they would jump in. They would immediately jump out if they heard the door opening. I finally tied fishing line to a dog’s cone collar of shame and set it next to the pool. I ran the other end of the line into the house. When they would approach the pool I would pull the line and the collar would scare them. It worked all winter. Currently, I have glittery beach balls in the pool, the cone collar still stands guard and I am thinking about buying a little remote controlled shark I saw on Amazon. If you come up with any better ideas, I would love to know.
Good luck!
this would be a good video 
