Found this on CSS tripadvisor website -

"From the three beaches (main, au natural and secret) to the various pools (main, au natural and mineral), to Charlie's grotto, there are lots of places tucked away to explore and enjoy."

Having been to CSS I was unaware of a 3rd beach presume that is why its 'secret' so I have just looked on the map of the site, Map & 360 View - Couples Resorts - is this beach the bit of white colour to the left of the mineral pool?