An emergency repair plug for sealing an opening in a boat hull, comprises a conical body made of a solid foam, spongy cellular material that is compressible by hand and able to return to its original shape. The conical body is compressible by hand to a smaller dimension so that a portion of the conical body larger than an opening to be plugged can be inserted into the opening. The conical body is able to return to its larger size after compression, thereby to be wedged in the opening to slow down water inflow through the opening.