A vessel (1; 101), the vessel comprising: - a hull (2; 102) having a moonpool (3; 103); - a firing line hoist system (5; 105), the firing line hoist system (5; 105) comprising - a tower (6; 106), which tower is arranged at said moonpool (3; 103), and is connected to the hull (2; 102) of the vessel (1; 101), and - a hoisting device (11; 111), which hoisting device (11; 111) comprises a load attachment device (12; 112), one or more cables (13; 113) and one or more associated winches (14; 114) to manipulate the position of the load attachment device (12; 112) relative to the tower (6; 106) in a vertical direction along a firing line (15; 115), which firing line (15; 115) extends through the moonpool (3; 103), wherein the hoisting device (11; 111) is adapted for raising and lowering equipment through the moonpool (3; 103); - a stationary main deck (38; 138) for storing equipment and/or tubulars; - a mobile working deck (19; 119), which working deck (19; 119) is configured to be moved between a working position and a transporting position, the mobile working deck (19; 119) comprising a front deck section (20; 120) having a deck opening (22; 122) for receiving the firing line (15; 115), and a rear deck section (21; 121) located adjacent the stationary main deck (38, 138); characterized in that the vessel (1; 101) further comprises: - a rear deck lift system for lifting and lowering the rear deck section (21; 121), independent of the front deck section (20; 120), between the working position and the transporting position, and - a front deck guide system for guiding the front deck section (20; 120), independent of the rear deck section (21; 121), in a substantially horizontal direction between the working position and the transporting position, wherein, when the working deck (19; 119) is in the working position, the front deck section (20; 120) and the rear deck section (21; 121) are located adjacent each other, with the working deck front section (20; 120) located above the moonpool (3; 103) and adjacent the tower (6; 106) such that the firing line (15; 115) extends through the deck opening (22; 122) of the working deck (19; 119), and wherein, when the working deck (19; 119) is in the transporting position, the front deck section (20; 120) is located above the rear deck section (21; 121) and adjacent the stationary main deck (38; 138). - a hull (2; 102) having a moonpool (3; 103); - a firing line hoist system (5; 105), the firing line hoist system (5; 105) comprising - a tower (6; 106), which tower is arranged at said moonpool (3; 103), and is connected to the hull (2; 102) of the vessel (1; 101), and - a hoisting device (11; 111), which hoisting device (11; 111) comprises a load attachment device (12; 112), one or more cables (13; 113) and one or more associated winches (14; 114) to manipulate the position of the load attachment device (12; 112) relative to the tower (6; 106) in a vertical direction along a firing line (15; 115), which firing line (15; 115) extends through the moonpool (3; 103), wherein the hoisting device (11; 111) is adapted for raising and lowering equipment through the moonpool (3; 103); - a tower (6; 106), which tower is arranged at said moonpool (3; 103), and is connected to the hull (2; 102) of the vessel (1; 101), and - a hoisting device (11; 111), which hoisting device (11; 111) comprises a load attachment device (12; 112), one or more cables (13; 113) and one or more associated winches (14; 114) to manipulate the position of the load attachment device (12; 112) relative to the tower (6; 106) in a vertical direction along a firing line (15; 115), which firing line (15; 115) extends through the moonpool (3; 103), wherein the hoisting device (11; 111) is adapted for raising and lowering equipment through the moonpool (3; 103); - a stationary main deck (38; 138) for storing equipment and/or tubulars; - a mobile working deck (19; 119), which working deck (19; 119) is configured to be moved between a working position and a transporting position, the mobile working deck (19; 119) comprising a front deck section (20; 120) having a deck opening (22; 122) for receiving the firing line (15; 115), and a rear deck section (21; 121) located adjacent the stationary main deck (38, 138); - a rear deck lift system for lifting and lowering the rear deck section (21; 121), independent of the front deck section (20; 120), between the working position and the transporting position, and - a front deck guide system for guiding the front deck section (20; 120), independent of the rear deck section (21; 121), in a substantially horizontal direction between the working position and the transporting position,