Most ocean surface waves are generated by the wind blowing over the surface of the sea, imparting movement to the water. They can be transmitted over thousand of kilometer of ocean, often losing little energy until they break upon a shore. Usually, they are less than 3.5 meters high. Waves more than 7 meters high are rare and those exceeding 15 meters height develop only during very severe storm.
The highest accurately measured sea wave was the one witnessed by an American ship USS Ramapo in February, 1933. While steaming from Manila, Philippines to San Diego, California, USS Ramapo reported a wave 34 meters (112 feet) high, from trough to crest. The height was measured by Lt. Fredric Margraff, one of the senior officers aboard the ship.