Excuse the vagueness of the question, I'm not sure how to word it. I'm interested in knowing what seafarers used to protect their skin from the sun throughout history around the world.
I've never read of a chemical sunscreen like we'd see today, but I have read of various oils and greases used to treat sunburn. In the period I study (during the Napoleonic Wars, roughly) most countries didn't have an official "uniform" for sailors, but in the British navy they were expected to make standardized-ish clothing out of cloth that was issued to them. They would wear loose trousers, a "round" jacket (that is, one without tails) over a shirt and a round hat while working, with extra clothes for colder climates. That would provide decent sun protection on its own, but uncovered areas (hands and feet in particular) would simply burn and then tan over time.
More answers are welcome, but this thread might be relevant to your question: Did sailors back in the day (say mid-1700's) have issues with things like skin cancer from excessive sun exposure?