Tom Scott has been cranking out his geography videos from California. On the heels of the musical road in Lancaster, http://www.neatorama.com/2017/10/16/Why-Californias-Musical-Road-Sounds-Terrible/ he tackles questions about sea level. How is sea level defined and determined? Why is sea level different in different places? How do land areas exist below sea level?
Scott does all this while in Calipatria, California, a town that is 55 feet below sea level. -via Laughing Squid