Bremont Watch Supermarine 300M Date Black Leather SM40-DT-SS-BK-L-S. Over the years, Bremont has developed its Supermarine diving watch collection to the exacting specifications required for professional divers and military personnel, working with the likes of the Royal Navy Clearance Divers, Special Forces Units, North Sea Deep Sea Divers and the Royal Marines. Bremont has also worked closely with open water swimmers, free divers, scuba divers and professional sailing teams to ensure our watches can be relied upon in any marine environment. We are proud to have created a collection of watches which is relied on by the best.