Moriches Bay (/mʊərˈɪtʃɪz/ mohr-ICH-iz) is a lagoon system on the south shore of Long Island, New York. The name Moriches comes from Meritces, a Native American who owned land on Moriches Neck.Two townships in Suffolk, New York (Brookhaven and the Southampton) share its shoreline.Moriches Bay is east of the Mastic Narrows and Great South Bay and west of Shinnecock Bay.