Wow, you did an excellent job explaining this. There are many places in Canada that are tidal. Where I live, the tides easily change 12 ft, so when we had logging camps down the coast we had to be aware of slack tide in order for the crew to leave camp. It was my job to fly a Robinson 22 helicopter (2 seater) and make sure the crew in the boat were a)headed the right direction, as it's easy to get turned around (and yes, I've had to hover at sea level in front of the boat and physically wave my arm and point which direction they needed to go :), and b) make sure they safely got home without a breakdown. Great post!