Perfect geometric circles up to 2m across, built in the sand at 10-30m, for years nobody knew what made them. They are the…Perfect geometric circles up to 2m across, built in the sand at 10-30m, for years nobody knew what made them. They are the courtship nests of a tiny white-spotted pufferfish, which spends days scraping radial ridges to funnel fine sand into the centre where the female lays. Watching a 12cm fish build one is extraordinary. The circles were photographed for years and attributed to everything from currents to aliens before Japanese researchers identified the maker in 2011 and described it in 2014 as a new species, Torquigener albomaculosus. Amami is a UNESCO World Heritage site (2021) and also home to Japan's most intact subtropical rainforest. Anchorage: Anchor in the sheltered bays; Naze port is the base. Hazards: Do not fin near the circles, the sand structure is destroyed by a single careless kick. Typhoons Jul-Oct. Plus