Remember when you got out of the water, your body was white all over with crusted salt? You couldn’t sink no matter what.
The lake levels fluctuate with the spring run-off, so if there was a lot of snow pack, the water will be less salty. However, in dry years, when the lake shrinks, the salt content is way up.
I guess they consider that pollution of sorts, so to avoid any problems, they just banned swimming. Kinda makes me wonder what they ever did with Saltair, the resort on the south end of the lake.