Mabata-bahari ni ndege wa maji wa nusufamilia ya Merginae katika familia ya Anatidae. Mabata hawa wanaishi baharini hasa nje ya majira ya kuzaa. Wengi wana tezi za chumvi maalum ambazo zinawawezesha kuvumilia maji ya bahari. Mabata-domomeno hupenda zaidi mazingira ya mito. Mabata-bahari hula samakigamba na gegereka wa chini ya bahari. Mabata-domomeno hula samaki. Meno ya madomo yao yanawasaidia kushika mawindo. Takriban spishi zote zinatokea kanda za kaskazini mbali. Melanitta nigra Bata-bahari Mweusi (Common Scoter) Mergus serrator Bata-domomeno Kidari-chekundu (Red-breasted Merganser) Bucephala albeola (Bufflehead) Bucephala clangula (Common Goldeneye) Bucephala islandica (Barrow's Goldeneye) Camptorhynchus labradorius (Labrador Duck) imekwisha sasa Chendytes lawi (Law's Diving-goose) imekwisha sasa Clangula hyemalis (Long-tailed Duck or Oldsquaw) Histrionicus histrionicus (Harlequin Duck) Lophodytes cucullatus (Hooded Merganser) Melanitta americana (Black Scoter or American Scoter) (pengine inafikiriwa kama nususpishi ya M. nigra) Melanitta deglandi (White-winged Scoter) (pengine inafikiriwa kama spishi ndogo ya M. fusca)