Clearest sea

The Weddell Sea, off Antarctica, has the clearest water of any sea or ocean. On 13 October 1986, scientists from the Alfred Wegener Institute in Bremerhaven, Germany, measured the clarity by lowering a standard Secchi disc, measuring 30 centimetres (1 foot) in diameter, into the water until it was no longer visible. In the Weddell Sea, the disc was visible until it reached a depth of 80 metres (262 feet) – a clarity similar to that of distilled water.