The Cancer Council recommends 35ml of sunscreen to be applied 20 minutes before exposure and 2 hourly thereafter except when swimming when it should be after drying off and to store sunscreen below 30C and definitely not in a car.
Think about it. Mum, dad and 2 kids go to the beach for the day, say 9 - 5. That means 4+ doses each (4 x 2 hours + 20 mins) using, say 1/2 dose for kids; 35mls x 4 x 3 = 420mls. But the kids, and mum and dad go swimming so need extra applications; even one more means a total of 560mls. At the Cancer Council shop charge of $39.95 per litre pack it is going to cost $22 for the day. And then the sunscreen has to be kept below 30C in the car and at the beach. Let’s hope the ice pack doesn’t melt too soon.
Practically, the recommendations are nearly impossible and too costly to follow. Sunscreens need to be able to be safely stored in a car and made much less expensive if they are to be used as recommended.
BTW Highlighting 4 hours water resistant on the front of the pack but recommending reapplying after swimming or every 2 hours is misleading.