The distance you can see on the ocean is primarily limited by the curvature of the Earth and your height above sea level. For an average person with eyes about six feet (1.8 meters) above the water, the horizon is roughly 4.5 kilometers (2.8 miles) away, which is the typical maximum visible distance at sea level under ideal weather conditions
. However, this distance can vary based on several factors:
- Height of the observer: Being higher above sea level increases the visible horizon. For example, from a ship's deck or a tall lighthouse, you can see much farther than from the waterline
- Height and size of the object viewed: Tall objects like lighthouses or cliffs can be seen from much farther away than small boats, sometimes up to 21 kilometers (13 miles) or more
- Weather and atmospheric conditions: Clear sunny days provide the best visibility, while fog, mist, haze, or pollution can drastically reduce it. Fog can reduce visibility to under 1 kilometer, mist between 1 and 5 kilometers, and haze varies widely
- Time of day and environmental factors: Light levels, humidity, temperature, and wind also affect how far you can see
In summary, while the geometric horizon for a person at sea level is about 2.8 to 3 miles (4.5 to 5 km), actual visibility can be greater if you are higher up or looking at tall objects, and it can be much less in poor weather conditions
