Furthermore the sun in a disc setting firmament or not will never look like it's going below the water from your perspective.

As the sun descends it will create a tangent into the horizon. The perspective lines nearly merge, causing the receding body to appear to intersect the horizon from the bottom up. Next the light of the receding sun is dimmed to blackness by a non-transparent atmosphere.

“ At these times it appears close to the horizon where the density of the air differs greatly. The air near the ground is denser than the layer of air just above it, and the layer of air above that is less dense still, and so on upwards until the Earth's atmosphere peters out at some 400 km. Now consider what happens when the Sun is setting. When the Sun is at the horizon, light from the top of the disc is going through the air at a different angle than that from the lower part. So the rays are bent by different amounts before they reach the observer's eye. The result is that the bottom part of the Sun's disc appears to be lifted up. In consequence the Sun's disc appears slightly compressed. ” —Samuel Birley Rowbotham