In 2021 Cuba revealed that its navy had a submarine. The existence of this mini-sub has been known outside Cuba for at least five years because of commercial satellite photos as well as cellphone photos taken in Cuba and showing up on the Internet. Until recently few other details of this sub were known. That has changed with the official announcement. The Cuban sub is called the Delfin and is similar to mini-subs built in Iran and North Korea. The Cuban sub is 21 meters (70 feet) long, has a crew of five. It is armed with one or two Russian torpedoes. A similar North Korean mini-sub sank a South Korean corvette in 2010. North Korea initially denied responsibility. South Korea recovered the sunken corvette and its dead crew as well as fragments of the torpedo which launched an unexpected attack on the corvette. The torpedo fragments were identified as North Korean and that incident ended decades of South Korean efforts to use “soft diplomacy” (food and economic aid) to persuade North Korea to make peace. Since 2010 South Korea has upgraded its submarine detection capabilities offshore and built a new class of corvettes better equipped to find and destroy North Korea subs. In the 1990s North Korea showed Cuban naval officers their minisubs. Back then Cuba was cooperating with North Korea to bypass the growing number of economic sanctions placed on North Korea. Both countries are communist dictatorships, perpetually broke and enemies of the United States.
The Cuban Navy was never considered much of a threat to anyone except Cubans trying to leave without permission. There are only two large ships in the navy, both elderly frigates armed with a 57mm gun and Cold-War era Russian anti-ship missiles. There are about a dozen elderly Russia fast patrol boats armed with torpedoes and some patrol boats that are civilian ships armed with machine-guns or a torpedo.
The Delfin was an unexpected development and appears to have been built locally a decade ago. Cuba also has about ten locally built SDV (Swimmer Delivery Vehicles) submersibles. SDVs are small submersible vehicles designed to take scuba-equipped naval commandos (like the U.S. Navy SEALs) from a submarine or small ship to a hostile shore. For over sixty years the World War II era Mk 8 SDV was the most widely used SDV. The Mk 8 is basically a reusable torpedo which divers in scuba gear hang on to as they are taken to shore. The MK 8 has long been used by American and British combat swimmers. Both nations are still using the MK 8 and despite all the new tech developed since World War II ended in 1945, efforts to design and deliver a workable replacement have not succeed until the 21st century. Many nations, including Cuba, still used SDVs similar to the Mk 8 but the new Cuban SDVs are based on a 1950s design, which put one swimmer in an open cockpit while other swimmers hung on. These SDVs were designed to carry the swimmers and some limpet mines or other weapons. These mines are built with magnets so they can be attached to enemy ships' hulls and detonate using a timer that enables the SDV to get away. The Cuban SDVs have a torpedo attached and the SDV has to surface, usually at night, so the torpedo can be aimed and launched at the target ship several kilometers away. This gives the SDV enough time to submerge and get away. Cuba will not discuss what its mini-sub and SDVs are for. The possibilities are endless.