Blue Lake / Warwar (The Blue Lake) is a large, meromictic, crater lake located in a dormant volcanic maar associated with the Mount Gambier maar complex. The lake is situated near Mount Gambier in the Limestone Coast region of South Australia, and is one of four volcanic crater lakes originally on Mount Gambier maar. Of the four lakes, only two remain, the other one being Valley Lake / Ketla Malpi; the other two, Leg of Mutton Lake / Yatton Loo and Brownes Lake / Kroweratwari, dried up as the water table dropped.
You will be looking for a non magnetic mint tin placed in the uprights along the Mannum pipline no need to climb under or over the pipe as the cache can be easily found on approach.