Inlet of the sea (3)
(Other definitions for bay that I've seen before include "laurel maybe" , "Botany, Galway or Tampa" , "Botany or Biscay, for example" , "Chestnut" , "Indentation of a shoreline" .)
(Other definitions for lagoon that I've seen before include "Almost enclosed body of water" , "Water cut off by coral reefs" , "Calm water behind reef" , "A slat-water lake" , "Shallow salt-water lake" .)