We disturbed a spoonbill roosting on the thrombolites. Musk duck calls out his territory in the water nearby.
These were quite squishy to the touch and birds had been pooing on them.
Close up of one of the lithified stones. I think this has been turned over when they dug the drain. It shows a non stratified texture. The brown fibres are fresh material dried on it from the last time the lake level was high. These whitish rocks are higher up the shore.