Huge container ship eclipsing the horizon. Nikon Coolpix P900.

Filmed in Galveston Texas the morning of January 29, 2017. Is the earth round or flat. This is a 140 foot tall container ship disappearing behind the horizon approximately 15 miles from shore? More or less. Average container is 8’6”-9’6” in height. I know this doesn’t take into account all factors but it may help some of you by providing useful info. It was just an experiment I did with my Nikon P900 with the 83x optical zoom.