Ewens Ponds
... that underwater visibility can reach 80 metres (260 ft) in the limestone sinkholes of Australia's Ewens Ponds?
... that underwater visibility can reach <span about="#mwt39" data-mw='{"parts":[{"template":{"target":{"wt":"convert","href":"./Template:Convert"},"params":{"1":{"wt":"80"},"2":{"wt":"m"}},"i":0}}]}' id="mwDGA" typeof="mw:Transclusion">80 metres (260</span><span about="#mwt39" typeof="mw:Entity"> </span><span about="#mwt39">ft)</span> in the <a href="./Limestone" id="mwDGE" rel="mw:WikiLink" title="Limestone">limestone</a> <a href="./Sinkhole" id="mwDGI" rel="mw:WikiLink" title="Sinkhole">sinkholes</a> of <a href="./Australia" id="mwDGM" rel="mw:WikiLink" title="Australia">Australia</a>'s <b id="mwDGQ"><a class="mw-redirect" href="./Ewens_Ponds_(South_Australia)" id="mwDGU" rel="mw:WikiLink" title="Ewens Ponds (South Australia)">Ewens Ponds</a></b>?