Answer: isobath

AnswerCrossword Clue
ISOBATHLine on oceanographic maps
ISOBATHConnector of equal ocean depths
isobathsimilar line for indicating the depth below the surface of the earth of an aquifer or the top of the water table
isobatha contour line connecting points of equal water depth
isobathimaginary line or one drawn on a map connecting all points of equal depth below the surface of a body of water