After changing the core bit, we struggled with a variety of problems today. The drill string had a swelled joint that had to be removed, groundwater flow at the bottom of the hole was driving away the drilling mud, and the rock in the hole kept collapsing in every time we pulled up to extract a run of core. Most of the rock recovered today was rubble or highly fractured, and this is the material that ruined our previous core bit. We will keep trying, and hopefully we will reach more stable rock soon.