The risks from over exposure to the harmful rays of the sun are both short and long term. Exposure is not only direct but often reflected from water, sand and snow.
Clothing is important.
Tightly woven fabrics are best. Many modern fabrics are designed to allow the passage of the sun's rays e.g. swimming costumes to ensure an even sun tan. Protect the head, ears, nose and neck by wearing a wide brimmed hat. This should be started at least 30 mins before exposure and be repeated immediately after swimming. The PF can be reduced as you become more used to the sun but do not stop using the sun cream.