Panama Canal:The Atlantic/Caribbean entrance to the canal is known as Gatun (ga-toon) locks. Many people seem to have some disorientation of direction as the canal actually runs from north to south. And of interest is that the Atlantic side is west of the Pacific side.
The locks use "mules" which are electric traction engines that guide the ships through the locks. Depending on the size of the ship, 4, 6, or 8 mules are used. Contrary to popular belief, the mules do not pull the ship through the locks, the ship goes through using it's own power.
The Gatun locks consisted of 3 levels, and the entire transit through the locks takes about 3 hours. The transit through the locks is tarrifed on the cargo capacity of the ship. For a passenger ship, it costs about $130 per berth, so they are among the most expensive fees for any ship.
Each time a ship goes through the locks, some 58 million gallons gets dumped from Lake Gatun to the ocean. Good thing Panama is a tropical climate with plenty of rain. The way the locks work is that all southbound ships (going from the Atlantic to Pacific) enter the locks - in both lanes. Then around noon, the direction reverses and the northbound ships are serviced. This changes again at 6pm and again at 12 midnight. The Panamax ships only transit the locks in the daytime, while smaller ships do so at night.