I’m watching overtourism in action. Within the iridescent marvel that is Croatia’s Blue Cave, four boats holding about a dozen people each have an allotted 10 minutes before we motor back out again so that the next batch of visitors can float in. About 1,500 people a day visit this beautiful grotto on the island of Biševo, the biggest attraction within the Vis archipelago, two hours and 20 minutes south of Split by ferry. After paying the €24 entrance fee, I’m left underwhelmed by this maritime conveyor belt. At least the 45-minute foot ferry from Komiža, on the archipelago’s main island of Vis, to Biševo’s Mezoporat Bay, the launch point for boats to the Blue Cave, is only €4.