Figure 5. Photograph of the traveling block in the derrick with the active and passive heave compensator cylinders (AC and PC, respectively) and swivel. The passive heave cylinders are by Western Gear, and the AHC system was added by Maritime Hydraulics at the 1999 dry dock. The core barrel and coring line are accommodated by a hole through the swivel and traveling equipment as well as a "split" crown.