Drilling data at site GeoB23213-1 were collected during operation of the sea floor drill rig MARUM-MeBo200 during research expedition SO266 in October 2018 on the summit of Formosa Ridge at the South China Sea. Vertical movements of the drill head are monitored with an electromagnetic encoder type TXN 11551 FD by TWK Supreme Sensoric GmbH. Drilling depth was calculated by summing up the drill head movements with the drill being connected to the drill string. The accuracy of the calculated drilling depth is about 0.1%. Flow rate of the flush water was measured within the pressure line of the flush water pump by using a RN3/32/15SP360 flowmeter by UK Flowtechnik. The accuracy of the measurement is better than 0.2%