As previously mentioned, the reaction of bodies of water with sunlight is very different from that of land. Being largely transparent, light penetrates deeply into water, so that the sun’s light is absorbed throughout a thick layer from the surface to some depth rather than just on the surface, as with land. Additionally, water has a high specific heat, which means that its temperature increases very slowly as heat is added. Consequently, water exposed to sunlight does not change temperature appreciably throughout the day, so there is no heating of air in contact with the water. If anything, during summer afternoons, when land is rapidly heating, bodies of water frequently are cooler than air temperature. The cooler water chills the air in direct contact with it, so the air lying just above water often is cooler than air higher up. Since air temperature normally decreases with height, this temperature reversal from the norm is called a temperature inversion. Temperature inversions are common over bodies of water during late spring and into summer. Since this temperature structure is the reverse of what causes inferior mirages, inferior mirages are far less commonly noticed over water. This happens particularly during the summer, when inferior mirages are common over land.
So the point is we have no idea what is below us. We can not dig down very far and find out. Or at least we have not dug down more than 7.5 miles so far… But if the earth is flat you could theoretically dig through it. But we have not dug down more than 7.5 miles, which is nothing compared to the 8,000 mile diameter they give for the earth…. So the point is we can’t dig down very far so we don’t know…
In consequence of the fact being so plainly seen, by everyone who visits the seashore, that the line of the horizon is a perfectly straight line, it becomes impossible for astronomers, when they attempt to convey, pictorially, an idea of the Earth's "convexity," to do so with even a shadow of consistency: for they dare not represent this horizon as a curved line, so well known is it that it is a straight one! The greatest astronomer of the age, in page 15 of his "Lessons," gives an illustration of a ship sailing away, "as though she were rounding the top of a great hill of water;" and there - of a truth - is the straight and level line of the horizon clear along the top of the "hill" from one side of the picture to the other! Now, if this picture were true in all its parts - and it is outrageously false in several - it would show that Earth is a cylinder; for the "hill" shown is simply up one side of the level, horizontal line, and, we are led to suppose, down the other! Since, then, we have such high authority as Professor Richard A. Proctor that the Earth is a cylinder, it is, certainly, a proof that the Earth is not a globe.
If we take a trip down the Chesapeake Bay, in the day-time, we may see for ourselves the utter fallacy of the idea that when a vessel appears "hull down," as it is called, it is because the hull is "behind the water:" for, vessels, have been seen, and may often be seen - again, presenting the appearance spoken of, and away - far away - beyond those vessels, and, at the same moment, the level shore line, with its accompanying complement of tall trees towering up, in perspective, over the heads of the "hull-down" ships! Since, then, the idea will not stand its ground when the facts rise up against it, and it is a piece of the popular theory, the theory is a contemptible piece of business, and we may easily wring from it a proof that Earth is not a globe.
In general, we at the Flat Earth Society do not lend much credibility to photographic evidence. It is too easily manipulated and altered. Many of the videos posted here to "prove a round earth" by showing curvature will show no curvature or even concave curvature at parts. The sources are so inaccurate it's difficult to build an argument on them in either case. Furthermore, barrel distortion and other quirks of modern cameras will cause a picture to distort in ways which may not be immediately obvious or apparent, especially without references within the picture. Photographs are also prone to distortion when taken through the bent glass of a pressurized cabin as well as atmospheric conditions on the outside. With this litany of problems, it's easy to see why photographic evidence is not to be trusted.
If the Earth were a globe, people - except those on the top - would, certainly, have to be "fastened" to its surface by some means or other, whether by the "attraction" of astronomers or by some other undiscovered and undiscoverable process! But, as we know that we simply walk on its surface without any other aid than that which is necessary for locomotion on a plane, it follows that we have, herein, a conclusive proof that Earth is not a globe.
3) The natural physics of water is to find and maintain its level. If Earth were a giant spinning sphere tilting and hurling through space then truly flat, consistently level surfaces would not exist here. There would be a massive bulge of water in the oceans because of the curvature of the earth. If earth was curved and spinning the oceans of water would be flowing down to level and covering land. Some rivers would be impossibly flowing uphill. There would massive water chaos and flooding! What we would see and experience would be vastly different! But since Earth is in fact an extended flat plane, this fundamental physical property of fluids finding and remaining level is consistent with experience and common sense. The water remains flat because the earth is flat!