June 21, 2017: The U.S. Navy has ordered its third Sealion (Sea, Air, and Land Insertion, Observation, and Neutralization) semi-submersible stealth boat. This is one of the many experimental boats created for the navy SEALs and SOCOM (Special Operations Command) to help get commandos ashore without being detected. Work on Sealion was always kept quiet, in part because work on the concept began in Israel during the 1980s and the U.S. Navy began working on a SEAL version in the 1990s. In 2003 the first of these Sealion boats was delivered. Sealion 2 followed by 2008 and both were quietly used for some SEAL operations. This led to Sealion 3, which is under construction for service in 2018.

All three versions of Sealion were between 22 and 25 meters (70-80 feet) long and weighing under 30 tons (light, no fuel or cargo). This light weight and small size was so the Sealion could be quickly moved by air (in a C-17 or C-5) to where it was needed. Once in the water the Sealion carried a crew of up to seven plus twelve SEALs and their gear. Sealion has radar and numerous other electronics but is built to operate without the radar on (or emitting any other signals that can be detected). The low slung Sealion is shaped to be difficult for radar to detect and all personnel and equipment (including one or two Zodiac landing boats) are stored inside with the personnel and equipment.

Sealion has apparently been used more and more frequently because of several failed efforts to develop an effective submersible SDV (SEAL Delivery Vehicles). SOCOM has been trying to develop a new submersible SDV for decades without success. These are small submersible vehicles to take SEAL commandos from a submarine or small ship to a hostile shore. In SOCOM did the unthinkable and placed an order for a militarized version of the S302 commercial submarine. This 27 ton vessel is called a DCS (Dry Combat Submersible) SDV. There is already a “wet” SDV but a DCS version has been long sought because it delivers SEALs to a hostile shore in better shape physically and psychologically to handle their mission on land. SOCOM has ordered three of these DSCs for $55.4 million each. Each DSC can carry a crew of two and six SEALs and their equipment. Max depth is 100 meters (320 feet) and max speed is nine kilometers an hour. Other specifications were not released but based on S302 capabilities the DSC will be carried on the deck of a nuclear submarine and can be entered from inside the sub and then released up to a hundred kilometers from shore and get the SEALs to land within ten hours.

Meanwhile the Sealion had made itself useful because every covert beach landing does not require a submersible. Exactly how many Sealions have been built is kept secret, as are details of operation. At the same time the Mk 8 SDV, which is a World War II era design that is basically a reusable torpedo which divers in scuba gear hang on to as they are taken to shore, is still available and in use. 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 in since World War II ended in 1945, efforts to design and deliver a workable replacement have failed so far. There were a lot of Mk 8 replacements that did not make the grade, all of them designed as military, not commercial, submersibles.

The most recent attempt for a purely military DCS was the ASDS (Advanced Seal Delivery Systems) which was abandoned in 2009 after it was discovered that fire damage suffered in 2008 to the only one built would cost $237 million, and take three years, to repair. SOCOM was reluctant to repair the vessel and decided to just walk away from the 21 meter long, 60 ton mini-submarine. Originally, the entire program (including six ASDS) was to have cost $527 million, but it ended up costing nearly twice that to only produced one. While a nice piece of engineering, each ASDS would have cost over $300 million. The U.S. Navy also spent $47 million building a base in Hawaii for the ASDS fleet. There, and in the Persian Gulf, the first ASDS production boat underwent testing for three years, before being declared ready for service in 2004. But problems kept cropping up, until the production of the other five was cancelled in 2006. After a decade of development, the ASDS had too many technical problems. Only the first one remained and it sort of worked until it caught fire.

Until 2015 there was still a military developed candidate; the SWCS (Shallow Water Combat Submersible). This was a smaller version of the earlier ASDS. Like the ASDS, the SWCS is battery powered, with a crew of two and carries about six SEALs. The larger ASDS could carry up to 14 passengers (fewer if a lot of equipment is being brought along, the usual number of passengers was expected to be eight.) With a max range of 200 kilometers, top speed of 14 kilometers an hour and max diving depth of 65 meters (200 feet), the ASDS was to operate from one of the seven U.S. nuclear submarines and several British boats equipped to carry it on the deck. Both ASDS and SWCS are equipped with passive and active SONAR, radar and an electronic periscope (that uses a video camera, not the traditional optics.)

In the end it was decided to find an existing mini-sub model that was cheaper and known to work. In 2015 it was hoped that SWCS would prove suitable but it wasn’t and now one of several suitable, serviceable civilian mini-sub models became the long sought DSC SDV.

Throughout all this Sealion and the MK 8 got it done, which is a lesson peacetime military equipment developers don’t like to hear.