Depends on how sunny it is that day
Keep a weather eye on the horizon means to watch the horizon or as far as you can look for ships=water, people=land or water, or an animal=land or water.
6.23 miles
You can see the horizon from any altitude on a plane. The horizon is the line where the sky meets the earth or sea, and it appears at eye level regardless of how high up you are.
The distance at which you lose sight of land when on water depends on factors such as your height above sea level and the curvature of the Earth. Typically, you can see land from a few miles up to around 12 miles offshore before it disappears below the horizon.
the horizon
The horizon. It is a imaginary line where land and sky appear to meet.
The distance to the horizon from the shore depends on the height of the observer's eyes above sea level. On average, a person standing at sea level on the shore can see approximately 3 miles to the horizon. If the observer is standing at a higher elevation, such as on a cliff or in a tall building, they can see farther.
They couldn't see any land because they were likely in the middle of a vast ocean or sea, where the horizon stretches endlessly in all directions. Additionally, weather conditions such as fog, rain, or clouds could have obscured any distant landmasses. It’s also possible that they were traversing an area that is far from shore, making land visibility unlikely.
It seems like 1,000,000,000,000,000 meters away
Our eyes can only see as far as the horizon, due to the curvature of the Earth. For instance, an observer standing on a hill 100 feet (30 m) in height, their horizon is at a distance of 12.2 miles (19.6 km). Obviously, without the restriction of a horizon, we can look out far into space on a dark night and see our moon and many stars and planets with the naked eye - even better with a telescope.
It Maybe B horizon or C horizon
That depends on the angle of elevation