nasa states the earth curve can be seen at 35,000 ft and you'll need a wide view. cameras have been up atleast 100,000ft and none was detected.
ships can see light houses atleast 20 miles away , using the formula for the earth curve , that lighthouse would be a more than 150 ft below the horizon.
your correct , only difference is the water is inside of the container , gravity solves this issue as many would claim , but there is one problem , gravity has the power to hold millions of tons of water stuck to the earth , but butterflies and insects go about their lives unaffected by the massive force called gravity.
RE: Question : At what height do we see curvature