This is the one I use:
Tide Tool for the PalmPilot
Its pretty simple. The curve illustrates the ebb and flow of the tide over each 24 hour period, the apogee of the curve is slack tide (e.g. tide is not moving in or out). You want to dive the slack.
One trick is to note the total rise/fall - it varies based on the phases of the moon.
Point is that some parts of the world experience drops of 11'-13' or greater during certain times of the month.
What does this have to do with you?
Visibility.
Look at any month of a charter boat schedule. Then look at your tide tables.
Some weekends the tide variance will be something like 2'-3'. Other weekends its 12'-13'.
(These numbers are examples, they will be different for you in Florida.)
The point is that you may experience much better visibility if you plan your diving during periods of relatively small tidal changes, rather than during weekends involving major tidal changes. This is because the higher amounts of moving water stir up sediment and particulate in the water.
You may be safer, also, because major tidal changes can involve a great deal of water moving over short periods of time, and (at least in the PNW) divers have been swept away by swift moving tidal currents that they misjudged.
FWIW.
YMMV.