The MDP has a large marine fleet of launches and rigid inflatables, divided between the three Naval Bases at Plymouth Devonport, Portsmouth and the Clyde. Their main task is to provide overt counter-terrorism policing to ensure the protection of HM Naval Bases, which includes undertaking high-profile armed patrolling of the waterfront. Each marine unit has a range of different operating conditions; those escorting the Royal Navy’s nuclear submarines operate in often difficult weather conditions on the Clyde, whilst at Portsmouth, escorting a huge 65000 tonne aircraft carrier through the naval exclusion zone where the carrier has priority requires the MDP craft to negotiate a busy sea channel carrying passenger ferries and commercial shipping.
Officers will work on both Rigid Hulled Inflatable Boats (RHIBs) and Launches, and are required to be trained to Royal Yacht Association (RYA) standards; this can range from Competent Crew to Coastal Skipper. Training in the MP7 weapon system and in marine-specific firearms tactics training is also required.
MDP Marine units also escort other surface vessels, including the vessels of visiting Navies, to and from the open sea. In recent years, MDP Marine Unit officers have been called upon to support the 2012 Olympics; the 2013 G8 summit in Northern Ireland; and the 2014 NATO Leaders' Summit held in Cardiff.