The curve of a body of water is something you can measure.
But I suppose you would reject as invalid any observation that disagrees with your FE notions.
This is hilarious. Who told you such a thing? Water surface ALWAYS settles flat. Aside from FE, curving surface of water is a farce. There is no empirical proof settled water surface curves or maintains curvature of any type. Water settles flat in my glass, in my pool, in the lake behind my house, and as described, in the glassy seas.