The horizon is as far away as you can see unless you look up at the sky or are as far out into the universe that the Earth shows as a true globe (if you don’t see the entire circumference of the Earth in one "take", the bit that’s left and unseen is really what makes the rest of the "picture" a horizon).

The horizon is the visual edge of the globe and most expressively so over water. The human eye is almost globular, and I don’t know if that’s why we perceive the double globular as straight and level even when it scientifically is not.

Water has a tendency to look level when it is "at rest", a faculty it shares with most liquids. A spirit level is a tool for builders and others to establish or confirm whether an object appears level with the horizon, and thus feels at rest and "right". A level spirit would be more esoteric, and perhaps a bit less pertinent to the subject at hand, although not wholly without tangent to this web site and my paintings.

At sea, the horizon is always a matter of earthly fact and of impact to your navigation or wellbeing whether you can perceive it or not (as when hidden from direct view by darkness, atmospheric or meteorological conditions). 
The sense of physical and often mental balance (equilibrium) is enhanced by one's perception of a steady horizon, whereas the lack of perceived equilibrium may cause mental or physical unease - in the latter case, seasickness.

A lifelong enthusiasm for being on, in or just looking at the sea, has ingrained in me the allure of the horizon. What lies beyond?
In my "soul" I'm not wholly comfortable without it.

Not surprisingly then, that I like to include a horizon in many of my paintings, be it somewhat obviously depicted in a seascape or just hinted at by a horizontal line in a more abstract piece. It makes me feel at home in the element of the physical or metaphorical salty sea, and I hope some of you who view these small or larger pieces of inspiration and efforts, can share the experience I try
to convey.