Is it possible to keep a metal ball that is enclosed inside a circular water filled tube circling the tube by means of a small attached inlet and outlet tube attached to a water pump for continued pressure ?

You could aramnge the inlet and outlet so that they cause the water to rotate inside the tube. Since the metal ball will sink to the bottom of the tube you could place the inlet tube near the bottom oriented to shoot water tangentially to the tube wall so as to push the ball, and the outlet near the top, above the top of the ball.