Line of Sight

do you mean the distance to the horizon? you can find that here:

http://en.wikipedia.org/wiki/Horizon#Distance_to_the_horizon

You need to know how far above the water your eyeball is situated and you need a transit or rudimentary protractor to measure the angle of inclination to the horizon. Then you have to know who Pythagoras was........

A rough rule of thumb, from my days at sea, is 48 feet above sea level, the horizon is approximately 8 miles ( on the ocean, that is)

Obenay N. Pebvk