SPF can fall by nearly 60% after 40 minutes in salt water

New tests show the effectiveness of water-resistant sun products plummet after they are worn in the sea or swimming pool.

Testing two popular brands, consumer group Which? found that the sun protection factor (SPF) of the creams dropped by nearly 60% in salt water.

The group claims industry testing guidelines are unrealistic as they use continually circulating tap water in a bath to simulate ‘moderate activity.’

The Which? test checked the water-resistance of the brands in controlled conditions, using chlorinated water, salt water and moving tap water.

tests saw the SPF of one of the products dropping by 59% in both salt water and moving water.

Tap water saw the SPF of one fall by 21% while the other fell by 40%.

Chlorinated water saw SPFs dropping by 21% and 40% respectively.

Image: Which?

The consumer group is not naming the firms involved.

It said guidelines around sun cream water resistance are “unrealistic to the point of being meaningless” and warns that consumers may be at risk in the sun.

Which? director of research and publishing, Nikki Stopford said the research raises serious questions about the current guidelines.

“Manufacturers should be required to robustly test their products and make only claims that can be relied on - ensuring holidaymakers know they can trust their sun cream to protect them,” she said.