It is based on the premise that an earthquake had catastrophically shattered the range of alluvial deposits separating the Imperial Valley from the Gulf of California, precipitating a tsunami moving north to transiently drown these lowlands.
[2] At the beginning of the story, Heinlein uses the character of a bartender in El Centro to establish the danger of the quake and inundation: You've heard about the 1905 flood, when the Colorado River spilled over and formed the Salton Sea?
Just imagine the shake-up it must have taken to drop thousands of square miles below the level of the Pacific.Heinlein's perspective character is a traveling businessman who had picked up two chance-encountered children and a vagrant while driving frantically to higher ground, and the dramatic arc centers on the efforts of the men to survive and save the youngsters from drowning.
[2] Although not tied directly to other of Heinlein's works, "Water is for Washing" is one of several short stories that take place in contemporary Southern California with no change in the political, social, or technological environment.
Robert Wilfred Franson describes "Water is for Washing" as packing "a neater punch than many whole novels of natural disasters and human reactions to them....As usual, Heinlein mixes a physical life-and-death challenge with considerations of knowledge, self-discipline, empathy, and spirituality."