In skincare discussions what you experienced is called "pilling" and it's the result of putting on a lotion or skin product too soon after another one that was applied too thickly or didn't have time to absorb fully. The balls are dead skin and the dried lotion or sunscreen that has gotten gummy and stuck to itself like eraser bits. Apply your sunscreen a little bit thinner and rub it in well and it shouldn't continue to happen.

If your shower routine is standing under water and just washing your stinky bits, chances are your body is still covered in sun screen. That stuff is designed to stay on in water. You need to properly wash yourself all over with soap/body wash and use a loofah. That will remove the sunscreen and also exfoliate dead skin.

Source: Australian

I'm assuming it has to do with your sunscreen and any other product you applied.