Abstract: A plastic hole cover unit includes a rectangular cover base of a dished construction with a continuous rim and internal support members which rest on the ice to cover the fishing opening. The base has a narrow diametric slot with sidewalls and extends from an edge of the cover to approximately the center. An integral cone-shaped post has a flat wall spaced slightly from and perpendicular to the inner end of the slot. A curved outer conical wall is integrally formed with the opposite side of the flat wall. The post has a small top opening which enlarges downwardly for significant exposure of the fishing opening for viewing of the water. The cover unit is formed of an opaque material to block light which could reflect off the water surface. A removable cap closes the top opening to trap the heat within the cover unit. The outer surface of the cover unit is provided with a black surface to increase radiant energy absorption and heating of air within the cover unit.