| Answer | Crossword Clue |
|---|---|
| waterline | line indicating the former level or passage of water |
| perpendiculars | An instrument for indicating the vertical line from any point, as a spirit level or plumb line |
| isobath | similar line for indicating the depth below the surface of the earth of an aquifer or the top of the water table |
| isobaths | similar line for indicating the depth below the surface of the earth of an aquifer or the top of the water table |
