Clearly tells the time of day and shows the hours to high and low tides. Attractive and Useful. Does not operate in the Gulf of Mexico Requires a single AA alkaline battery Scratch-resistant acrylic lens Time and Tide Clocks are useful and exciting additions to any coastal home. They are perfect for swimmers, beachcombers, fishermen, surfers and boat owners, offering a simple and reliable way to tell the time of the local tides, along with time of day ---at a glance.The tides run on moon time, where each day has 24 hours and 50 1/2 minutes, so high and low tides do not occur at the same hour each day. The Time and Tide Clock clearly shows you both tides and the time of day. Time and Tide Clocks are much easier to read than printed tide tables, and come in a variety of styles to compliment any decor. Tide Clocks do not operate in the Gulf of Mexico.