A float boom for confining material floatable on a liquid surface during high temperature conditions, comprising: an elongated floatable tube formed of fluid impervious material; a source of fluid under pressure for cooling the boom during high temperature conditions; piping connected to the source of cooling fluid for distributing the cooling fluid over the length of the boom; and, a protective cover, of a fluid-absorbing material, mounted over the tube, the cover having peripheral edges adapted to engage the boom to encase the tube therein, the piping distributing the cooling fluid over the tube and under the cover to soak the cover over its length.