This sturdy metallic "action toy" was a present (a few years ago) from my daughter. The whale stands with its fins on a wave platform and a good downward push on the tail results in its swinging up-and-down — the curved water-appendage to-and-fro, pendulum-like. The disarticulated lower jaw - eye - blowhole waterspout provides the action as that single piece (sandwiched between two plates that comprise the body of the whale) sways out-of-synch with the overall motion.

This whale was apparently manufactured in Indonesia: The paint has come off in a couple of spots — still, it's a very nice object. (I'm using it as a deterrence-device to dissuade Hazel from getting behind the cabinet that supports the living-room television.) A jumping-jack is another toy that relies on relative motion as its entertainment mechanism.