You need a height of tide of 4.0 m to get over a marina sill. Reading this curve, when does the rising tide reach it?
A graph of height of tide against time, on a grid with a line for every metre and every hour. The curve rises in a smooth S shape from low water of 1.0 m at 0600 to high water of 5.0 m at 1200. A gold dashed line runs across at 4.0 m.
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1000. Go across from 4.0 m on the height scale to the curve, then straight down to the time scale: 1000. The curve is steepest in the middle hours, which is what the rule of twelfths approximates.
