Buster is married with two children (both of whom wear the porkpie hat made famous by Keaton). He has built a large boat he has christened Damfino inside his home. When he finishes and decides to take the boat out to sea, he discovers it is too large to fit through the door. Buster enlarges the opening a bit, but when he tows the boat out, it proves to be a bit bigger than he estimated, and the house collapses, utterly.
Buster loses his car during the attempt to launch the boat. The boat passes with impunity under the exceedingly low bridges of the Venice (California) canals thanks to Buster’s boat design. While out on the Pacific, Buster and his family are caught in a terrible storm. The boat is barely seaworthy to begin with, and it does not help that Buster nails a picture up inside the boat, causing an improbable leak, or when he further drills through the bottom of the boat to let the water out (resulting in a spectacular gusher of a leak). He radios a Morse Code call for help, but when the navy or coast guard operator asks who it is, he answers, “d-a-m-f-i-n-o” (in Morse Code). The man interprets it as “damn if I know” and dismisses the call as a prank. Taking to a (ridiculously small) dinghy (that is in fact a bathtub), the family resign themselves to the fact that they will sink into the sea, only to discover that the water is in fact only two feet deep. After a short walk through the water Buster and his family happen upon a deserted beach in dark of night. “Where are we?” asks his wife (via an intertitle), to which Buster replies, “Damn if I know” (mouthing the words to the camera, no intertitle is used).
Edward F. Cline and Buster Keaton / First National Pictures [Public domain], via Wikimedia Commons