I'd envision a torso and neck wrap of buoyant material, kind of a horsie life vest, with a tether to keep the horse far enough away from the edges of the pool such that if it kicks upon awakening it cannot kick anything hard.
In this photo provided by the University of Pennsylvania, Dr. Dean Richardson controls Barbaro as the horse is transported from the pool following surgery at the George D. Widener Hospital for Large Animals at the University of Pennsylvania's New Bolton Center Sunday, May 21, 2006, in Kennett Square, Pa. (AP Photo/University of Pennsylvania, Sabina Louise Pierce)
Don't you know it felt good for him to wake up with at least his "ankle" back in its "socket," even if he did have a bunch of plates and screws attached to his bones?
That dislocation just had to be the most painful part. The doc said the fractures didn't break the skin, which was also fortuitous for Barbaro.