Karikari's popular 'Coca-Cola Lake' closed due to toxic bloom 6 May, 2021 05:00 PM 3 minutes to read An algal bloom at Lake Rotopotaka as seen last summer. Photo / supplied Peter de Graaf is a reporter for the Northern Advocatepeter.degraaf@northernadvocate.co.nznorthernadvocat A popular freshwater swimming spot in the Far North has been closed due to an algal bloom which can make people ill and is lethal to dogs. Lake Rotopotaka, a dune lake on the Karikari Peninsula in Doubtless Bay, is a busy cooling-off spot in summer and a year-round tourist attraction due to the dark brown colour of the water.