It is zinc, a thick sunscreen that basically just literally covers the skin. I’d suspect that given the time spent outside, some of the guys apply sunscreen regardless of the actual weather, also it’s not like they can just nip in and grab some if the weather clears up.
UV radiation can pentrate cloud cover fairly efectively - the worst sunburn I ever got as a child was on a cool, cloudy day when I spent the whole day messing about with a mate on a canoe with no shirt or sunscreen on.