How can we see boats beyond the geometric horizon at the beach?

[DaveC426913]

And how high are your eyes above sea level?

Total distance of 51km.

Water tower is about 80 feet tall. (at least it was. It seems to be missing now.)

On a good day I can see it from the Islington bridge, which is maybe 40 feet high.
On a very good day, I see see it from the shoreline (15 feet).

For a long time I toyed with the idea of going out every few days for a year to the exact same spot and taking a pic of the horizon with some referencible landmarks in view - just to show a montage of the horizon in varying temperatures and seasons. (I may have waited too long.)

 

[DaveC426913]

This is what happens when the job is given to an artist, who misses the entire point. Most of the ship, especially the chimney for which the light path is shown, are not beyond the horizon anyway.

It gets the point across.

It would be very difficult - and not very informative - to try to render this to-scale.

And, I confess, there is an extreme paucity of such diagrams out there. This is the best I could find.