Read a tide table and apply the Rule of Twelfths to calculate the height of tide at any time between High Water and Low Water. Work through NOAA and Admiralty tide table formats, find the tidal range, use the secondary port difference method to correct predictions for non-standard ports, and calculate the available depth under a fixed bridge at a given state of tide.
Tidal calculations appear in the USCG Nav Problems module at every licence level and are a practical necessity for any vessel operating in tidal waters. The Rule of Twelfths is the fastest mental arithmetic tool for under-keel clearance decisions.