I've only ever used factor 50 in the mountains for my face, using factor 50 on the beach you might as well just sit in the shade if your going to burn that easily!
Its not though. Say you burn in 10 minutes normally, factor 50 is still only going to give you 8 hours protection.
Plus most research shows that people do not apply enough of any particular cream so only end up with a factor a third of what the bottle should cover eg SF15 applied in small quantities would only give you SF5 and even SF50 would only give you 16. It's recommended that an adult use a full handful to get the protection as stated on the bottle.


Shiver me timbers.