Fred Miller wrote:
I know that the peak or trough of a tide is not linear with time but I can't
remeber if it is 1/6, 2/6, and 3/6 for each of the three segments or if it
si different. Can anyone help, please.


Yes, you have it sort of right, but not quite. Its often called the
"Rule of Twelves." One twelfth of the height come in in the first
hour, two twelfths in the second, three in the third, three in the
forth, two in the fifth, one in the sixth. Thus the fastest change will
occur at mid tide.

Sometimes the Rule of Twelves is applied to currents, but that is often
not correct. When the current is caused by large bodies of water of
differing heights connected by a narrow channel, the current gets up to
speed rather quickly - sometimes reaching half speed in less than 30
minutes from slack tide.