Living in Cornwall I am used to clear blue-green seas reflecting summer’s every mood, but nothing had quite prepared me for how clear the Adriatic around Croatia is. It’s beautiful, mesmeric, unparalleled… but why?

The first thing to understand is that Croatian beaches are not sandy. The island of Lopud is the exception, but even so, the sand is not as we would understand it in the British Isles, with the swathes of flat golden beaches we love. If you expect these on your Croatian holiday, then think again. To Croatians a beach is more often than not a wide ledge of rock you can dive off into the sea.

The Dalmatian coast and its islands have particularly clear water. In large part this is down to the natural geography and geology, because the major rivers in the region, such as the Neretva and Cetina, have wide deltas so deposit their sediment there. In addition the coastal rocks are particularly hard so do not fragment when they erode (see lack of sand above!), which leaves the water devoid of visible particles.

All the same, this all could have been ruined by industrial development. Coming out of communism, Dubrovnik in particular had a choice; oil refinery or tourists? Thankfully they chose the latter, and today Croatia, Italy, Slovenia and Montenegro are part of a joint commission to ensure the beautiful waters of the Adriatic remain as free from pollution as possible.