The downfall of My Water Lily 

What happens to my Water lily? The leaves are almost all gone and the tadpoles have insufficient shades to hide!

For the past two weeks, raining had been too frequent and the water level was continuously full in the pond about 1.5 feet above normal level. I did not bother to drain, thinking that the plant is a water plant, submergence would not be a problem. But when I went to check a few days ago, poor water lily, half dead already! I drained away the water hoping it would survive again. 
It appears that the plant can only grow well in constant low water level or muddy soil environment.