Russia's state-of-the-art non-nuclear Piranha type submarine P-750B is equipped with a pressure equalisation chamber for simultaneous entry and exit of six combat divers, Igor Karavayev, the designer of the submarine said. For the first time, the Piranha type submarine P-750B with an airless propulsion plant was presented to the general public in June of 2019 at the naval show in St. Petersburg. The submarine had the pressure equalisation chamber which makes it possible to covertly land and take on board naval special forces. With the help of this chamber, six combat swimmers can go on a mission at a time. The airless propulsion plant also increases the stealthiness of the submarine. The submarine can thus stay under water without the need to surface for battery recharge. The displacement of Piranha-class submarines P-750B will be increased almost four times, while its crew will double. To crown it all, the submarine will be armed with Caliber cruise missiles. The submarine can be armed with torpedoes, mines and even Caliber cruise missiles that are launched horizontally from under the water. The P-750B is an initiative development by Malakhit Design Bureau. The company is ready to offer the new development to the Defence Ministry and potential foreign customers. In 2017, it was reported that Iran evinced interest in Russian Piranha type small coastal action "P-650E" submarines.