Nick wrote:
The horizon depends on the height of your eye - the dipping distance
tables in the almanac give the distance off for height. You will see

objects above sea level 'over the horizon' according to their height
so
as the ship approaches, you will see more of it.

70 foot high ship viewed from 3 metres high. I can't be arsed to do the
maths but I bet it isn't *far* off 22 miles.

What would you estimate?