We have an unknown older portable course permanently installed on public water. Just my buddy and I ski it, his house is within sight of the course so he can keep an eye on it. On February 28 I replaced all the balls, by June 1 50% of the balls sunk. I replaced those balls, and in 6 days, 3 of those sunk. My original set were Overtons and Polyform, kinda mis matched to see if one would last longer than the other even though they seem to be the same ball. What I'm seeing appears not to be vandalism but rather stress caused on the ball or maybe a caustic action from acidic water? The bottom half of the ball that's exposed to water is developing holes, but not smooth pin holes like somebody poking/popping them, and every hole has same size shape characteristic and consistance making me doubt vandalism more.
What we have is typical course suspended in 6' of water on one end, probably 10' the other. the course is sitting about 6' deep, with 3' or so rope coming from the pvc arms, then a 3' or so (stretched) cheap 5/16 bungee cord attached to the ball. the balls seem to sit about the same elevation in the water as the needle hole.
Does this ball life seem normal? Could we have too much weight hanging on the balls? Over/under inflated balls? Thanks for the opinions.