For removably coupling a boat apparatus, such as a boat table or seat, to a boat deck, a base plate having an arcuate or curved clamping slot is attached to the boat deck and the table or the like is securely coupled to a base assembly having a downward extending clamping device. The base assembly is placed on the base plate with the clamping device engaged in the clamping slot and the base assembly is then twisted or turned so that the clamping device slides to the end of the slot and a member on the base assembly is then manually operated to releasably clamp the clamping device securely in place in the associated slot.