What will the marking on the ship's water line show?
30 feet. Ships float, so the rising tide won't make a difference.
-- "Theology is never any help; it is searching in a dark cellar at midnight for a black cat that isn't there. Theologians can persuade themselves of anything." -Robert A. Heinlein
oic. By taking exactly 10 pennies, whatever the amount of heads there are showing in that pile, the amount of tails showing in that pile plus the amount of heads showing in the other pile equals ten!