A lagoon on the Baltic coast of Germany, within the provinces East and West Prussia, between Danzig and Konigsberg. It is 52 m. in length, from 4 to 12 m. broad, 33 2 sq. m. in area, and is separated from the Baltic by a narrow spit or bank of land. This barrier was torn open by a storm in 1510, and the channel thus formed, now dredged out to a depth of 22 ft., affords a navigable passage for vessels. Into the Haff flow the Nogat, the Elbing, the Passarge, the Pregel and the Frisching, from the last of which the name Frisches Haff probably arose.