Abstract: A mooring station and transfer terminal for offshore hydrocarbon production comprises a watertight caisson topped by a rotatable arm which supports a pipe for loading oil tankers. The caisson houses manifolds and a T F L (Through Flow Line) switching device connected to the different underwater producing wellheads. A T F L - servicing pipe supported by the rotatable arm and connected to the switching device through a rotary coupling at the top of the caisson permits introduction of T F L tools or instruments from the water surface into a selected well through the switching device.