Abstract: A depth measurement apparatus for measuring the depth of a hole and/or the depth of any liquid or slurry in the hole. The depth measurement apparatus comprises a spool containing a length of cord having a bob attached to a free end of the cord remote from the spool. The bob is a solid body, preferably being in the shape of a sphere, a spheroid or an ellipsoid. The apparatus has a measuring device arranged to measure a length of the cord dispensed from the spool during use, which indicates the depth of the hole. The measuring device is also arranged to measure the acceleration rate at which the cord is dispensed from the spool, wherein a change in the acceleration rate indicates that the bob has entered a liquid or slurry.