I read a about a Rule of Twelfths which could guide my session times based on the water level rather than simply going at high tide. What do you think? Sorry for being such a geek...but I am a tech guy!

Wikipedia explanation....
The rule of twelfths[1] is a rule of thumb for estimating the height of the tide at any time, given only the time and height of high and low water. The rule assumes that the rate of flow of a tide increases smoothly to a maximum halfway between high and low tide before smoothly decreasing to zero again and that the interval between low and high tides is approximately six hours. For the six hours, the rule says that in the first hour after low tide the water level rises by one twelfth of the range, in the second hour two twelfths, and so on according to the sequence - 1:2:3:3:2:1.
Example Calculation
If a tide table gave us the information that tomorrow's low water would be at noon and that the water level at this time would be two metres above chart datum and further, that at the following high tide the water level would be 14 metres. We could work out the height of water at 3:00 p.m. as follows:
*The total increase in water level between low and high tide would be: 14 - 2 = 12 metres.
*In the first hour the water level would rise by 1 twelfth of the total (12 m) or: 1 m
* In the second hour the water level would rise by another 2 twelfths of the total (12 m) or: 2 m
* In the third hour the water level would rise by another 3 twelfths of the total (12 m) or: 3 m
*This gives us the increase in the water level by 3:00 p.m. as 6 metres.
This represents only the increase - the total depth of the water (relative to chart datum) will include the 2 m depth at low tide: 6 m + 2 m = 8 metres.