That the Earth’s surface is 70% water, that surface MUST be flat!
With the earth’s surface connected waters being about 70% and the rest 30% being continental landmasses [cf. UNIVERSE TODAY > Earth Surface] and given the properties of water like water seeking its level hence the term and datum “sea level”, the earth’s surface must be flat.
Cf Heliocentrism CANNOT shed Ancient Concepts of Cosmology