This escape took place on June 30, 1917 in Westport (Saugatuck), Connecticut, during a special Red Cross charity drive at the home of Frederick E. Lewis II. Houdini is being lowered into Long Island Sound here. The below from the June 27, 1917 Bridgeport Times announces the event and Houdini's escape.
At the moment, this is Houdini's last known public overboard box escape.
Thanks to David Copperfield and the Westport Museum for History & Culture for their help solving the mystery of this famous footage.