Honestly, I am grossed out by very few things. However, I agree with the public hot tub thing. I visualize the contents of the tub being about 80% water, 10% sweat, 5% pee and 5% sunscreen, all heated to a rolling boil, waiting for your enjoyment. Perhaps there's a drop or two of Chlorine that still remains trying to kill off that other 20% non-water stuff.
I went into the one at AKL, alone, very shortly after the opening of the resort. I figured it hadn't had a chance to get nasty yet. But, when I see the hot tubs, loaded to capacity in the middle of a hot day, that stick in the eye starts looking really good.