You are wise to be concerned and to protect yourself from the beginning.
We are fair skinned of English ancestry.
We raised three fair skinned daughters on-board all of whom wanted a tan. Luckily, while they were adolescents a lady cruiser friend said to them, "Have a good look at my old wrinkled skin. If you want to look like me in a few years just keep up trying to get tanned."
We have lived aboard and cruised for 35 years, most of it in the tropics.
The first mate is an RN and was always serious about avoiding melanoma.
Recently a Stanford Univ dermatologist gave us a nice compliment. When he saw on his schedule an examination of a long term cruiser, he decided to use it as a teaching situation and brought with him his medical students. He took one look and said, "Your intake form claims decades in the tropics. Is that right?"
We answered that it was correct.
He said, "Well, I'm very surprised at the excellent condition of your skin. We can obviously use you as an example of how to properly care for one's skin in the tropics."
Sadly, there is no easy solution but this is what works for us.
Research skin damage from the sun, especially melanoma. See a dermatologist and get a briefing about your particular type of skin.
We are aware of solar damage every day light hour -- plan for it.
Yes, we wear large brimmed hats with a means to keep them on in high winds.
We like light weight cotton clothing that covers arms and legs.
While snorkeling we wear something that covers our backs including the backs of our legs.
Any skin showing should be covered with high SPF sun screen -- regularly. Carry sunscreen with you. Apply at least 30 minutes before going into the sun.
Keep sunscreen in the cockpit and the dinghy, purse and backpacks.
Since sunscreen is costly we buy the highest grade we can find and then mix it with inexpensive body lotion to the percentage we desire.
There are places that are easy to miss while applying sunscreen:
The backs of hands.
Ears, especially the tops.
We think cockpit biminis and side curtains are essential at sea, while generous awnings are a must at anchor.