Ren Mar is a fake beach town in Southern California, close to the Mexican border. It was home to Andy Botwin's Grandmother, Bubbie, before she passed. The Botwin Brothers, Judah and Andy, were brought up in Ren Mar. Also the birthplace of Stevie Ray Botwin.
A local Ren Mar teenager, Rad, remarks that whenever he swims in the ocean he gets a rash, alluding to the poor water quality near the San Diego-Tijuana border from industrial, agricultural, and sewage pollutants in the Tijuana River.
Locals believe that Ren Mar may represent Del Mar, California.