English: REMUS Unmanned Underwater Vehicle Used for Mine Countermeasure (MCM) operations on-board HMS Hurworth during REPMUS 22.REPMUS (Robotic Experimentation&Prototyping augmented by Maritime Unmanned Systems) is a Portuguese Maritime Operational Experimentation Exercise, which takes place annually. It was established as simply REP in 2004 and grown year on year. In 2014 NATO CMRE were invited to take part for the first time and then an invitation was issued in early 2019 for NATO’s Maritime Unmanned Systems Initiative (MUSI) to take part, which they did later that year and again in 2021 and this year. (2020 did not occur because of the global pandemic) providing a significant boost to the scope and scale of REPMUS.REPMUS is a testing ground designed to allow a large-scale experimentation where NATO navies can collaborate with each other and with Academia and Industry to develop and test unmanned system capabilities, to build interoperability&interchangeability and to develop operational concepts, tactics, techniques and procedures.