What percent of the boat is visible?

If the water surface is found from a globe earth than the lower portion of a boat should gradually disappear even when observed through a telescope or binoculars or video magnification now I have seen videos where a boat disappears until it is zoomed in on through a telescope but on a round earth with a round water surface the boat would still re appear when zoomed in on by a telescope but a gradually increasing portion of the bottom should disappear until the whole boat is gone however on a flat earth with a flat water surface the same percentage of the bottom of the boat should be present when zoomed in on.  I am impressed by the videos of a boat reappearing when zoomed in on but I want to know if the percentage of the boat visible decreases as less of the bottom can be seen indicating a globe earth with a curved water surface or if the percent remains unchanged.

Copyright Carl Janssen 2019 October 5

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