S103 was commissioned by, and is still operated by a Portuguese science foundation, FRN, based in the Azores.
It is a diesel electric submersible which provides comfortable seating for a crew of three with ample space for science equipment. The bow features a spectacular full diameter 150° spherical sector window.
The main electric motor is driven as a generator by the diesel while on the surface to recharge the battery and a high pressure air compressor is clutched in to recharge the air bank.
S103 is fitted with four hydraulic manoeuvring thrusters, a 5 function manipulator, which stows inside the crash bars, underwater lights and camera equipment.