Abstract: An oscillating wave-type lawn sprinkler is provided of the type having a water-powered drive mechanism for angularly oscillating an elongated spray tube generally about its own axis, wherein the drive mechanism has a crank link coupled to the spray tube by an improved releasable coupling assembly. The releasable coupling assembly comprises a C-shaped clamp at one end of the crank link, sized to fit around the spray tube, an indentation in the spray tube, and at least one tab on the interior surface of the clamp for releasingly engaging the indentation. During normal operation, the tab is engaged in the indentation and the angularly oscillatory motion of the crank link is imparted to the spray tube. When the spray tube is subjected to an external rotational force exceeding a predetermined magnitude, the spray tube rotationally disengages the indentation from the tab to move independently of the crank link, thereby preventing damage to the drive mechanism.