The Tides of Fundy

English: , The tides in the Bay of Fundy are among the highest in the world, reaching 16 m (53 feet) at the head of the bay. Closer to the mouth, the tidal range is less. At Saint John it averages 7 m (23 feet), still enough to make this the port with the world's highest tides., These exceptional tides are due mainly to the particular length and depth of the Bay and adjoining Gulf of Maine. Water can be made to rock back and forth (and up and down) in this system, as in a bathtub. The natural rhythm of such a rocking wave in the Bay is about 13 hours. This is close to the rhythm of the ocean tides, which sweep along the Atlantic coast every 12 ½ hours. In so doing, they amplify the Fundy tides, like an adult making a child go higher on a swing by pushing at just the right time. , For the port of Saint John, the berthing and departure of larger vessels has to take place during the “tidal window,” the time either side of high tide, about five hours in total, when the water depth is greatest. Smaller vessels that draw less than 8 m (28 feet) can enter and depart at any time. , The movement of vessels in and out of the harbour is controlled by the Harbour Master, who keeps track of all vessels that want to use the harbour, their planned arrival and departure times, the water depth they require, and how long it will take them to make their passage. Using this information, along with data on the time of the highest tides, the Harbour Master ensures that all vessels arrive and depart safely., For more information on this subject, please visit the New Brunswick Museum. ,