Living out here as a kid, then always in and out of the pool all day long, never wore Sun tan lotion, despite the looks of someone of the Ayran race, and never got burnt. My dad on the other hand, used coconut oil and was, to coin an old British saying, as black as the ace of spades.
However, noticed in my 20's taking European holidays, ie 2 weeks of as much sun as possible, then did get burnt, so started to use the old SPF 8 or 15 on the face. Only time I got seriously burnt was on my feet, as they were covered in sand, so assumed they were protected, couldn't walk for 3 days!
Did some research into SPF's at the time (1980's), and longevity was based on 15 minutes, so SPF 8 was rated to protect for 2 hours. So came up with the theory of total exposure for 15 minutes, then spent the rest of the day under cover. Always got a good tan after the 2 weeks. Also added a good smothering of moisturiser to the face at the end of the day.
Looking at the ingredients of today's Sun tan lotions, they contain half the contents of a pharmacist's laboratory. So wouldn't use them.
Nowadays, adopted the Aussi mantra of "Slip,Slop,Slap", although without the Slop.