This paper proposes an extensive model for unmanned underwater vehicle operations in aquaculture and includes a dynamic 6 degrees of freedom (DOF) quaternion-based model of a remotely operated vehicle (ROV) and a model of a net cage structure. The proposed vehicle and net cage models are subjected to waves and a dynamic current flow, which itself is affected by the wake effects from the net cage. Furthermore, two ROV platforms with complete sets of dynamic parameters are presented, the Argus Mini ROV and the BlueROV2 underwater vehicle. The suggested models are tested for aquaculture operations in simulations using the Argus Mini ROV as the test case in the vehicle model. The simulations demonstrate a net following procedure where the vehicle is exposed to various degrees of environmental effects from waves and currents.