The question does not ask about how far can the eye see on a curving surface. The asker stated 'a flat surface' Since when in mathematics do we mix up a flat surface with a curved surface. You have turned a very simple question in to a complicated question by introducing a curved plane.
As one would expect, the further you travel from the Equator, the colder the ocean waters generally become. Near the Equator, surface water temperatures can be as high as 80Â° Fahrenheit (27Â° Celsius). Near the poles, the temperature drops to a chilly 28Â° Fahrenheit (-2Â° Celsius). The western side of oceans are usually warmer than the eastern side. This is due to the way in which both the atmospheric and oceanic currents move water from the equator towards the poles on the western side of oceans, and from the poles towards the equator on the eastern side of oceans.
Ocean water differs in temperature and salinity. Warm surface water is generally saltier than the cooler deep or polar waters., in polar regions, the upper layers of ocean water are cold and fresh.Deep ocean water makes up about 90% of the volume of the oceans.Deep ocean water has a very low temperature, typically from 0-3 Â°C (32-38 Â°F), and a salinity of about 3.5% or as oceanographers state as 35 ppt (parts per thousand).eep ocean water has a very low temperature, typically from 0-3 Â°C (32-38 Â°F), and a salinity of about 3.5% or as oceanographers state as 35 ppt (parts per thousand).