A Supply Vessel was discharging cargo alongside a MODU. The main block was being used in conjunction with a heavy lift pendant line. During the operation the Deckhand, in his normal course of operation, handled the pendant line to disconnect / attach the hook. In carrying out this activity he sustained deep cuts to his left hand and thumb. The vessel ceased operations and returned to harbor to get the IP to hospital. Following medical treatment the IP was discharged from hospital but will be unfit for work for an extended period. This has been classified as a Days Away From Work Case (DAFWC).