Unmasking The Columbia River's Mysterious Stealth Boats

For about a decade there have been sightings of some very peculiar high-speed watercraft patrolling up and down the Columbia River between Portland and Vancouver. It just so happens that these phantom vessels are some of the US Navy SEALs newest toys.

Unmasking The Columbia River's Mysterious Stealth Boats

The origin of these boats remains somewhat shadowy, but it would seem that they evolved from a concept initiated by the Israeli Special Operations community in the late 1980's. Patents filed in the 1990s show the design would become "the Alligator," a semi-submersible, high-speed special forces delivery, extraction and reconnaissance craft that features a very low radar cross-section. All known accounts state that the Alligator was first launched in the mid 1990s and was said to have been tested briefly by the US Special Operations community before being delivered to Israel. The number of alligators built remains a mystery.

Unmasking The Columbia River's Mysterious Stealth Boats

The already low-slung Alligator has the ability to lower its draft to the point where the cabin windows sit right above the waterline via flooring ballast tanks located on each side and below the boat's main cabin. This results in the boat not only being very hard to spot on radar but it is also challenging to spot visually. The streamlined hull and low drag design, along with some powerful water-jets, allow it to move at high speed, especially when its ballast tanks are empty.

Although I have had some trouble getting a confirmation on it, it seems that Oregon Iron Works, a locally well known metal fabrication firm, has been involved with building the Alligator since its inception and continues as the prime contractor for constructing not only the Alligator Class but also its follow-on Sealion and Sealion II Class.

Unmasking The Columbia River's Mysterious Stealth Boats

The Sealion project, which stands for SEAL Insertion, Observation and Neutralization, began in 2000 as an experiment between the US Navy's Surface Wafare Command and the Naval Special Warfare Command. The idea was to test a larger, more multi-role oriented version of the Alligator, one that would feature a much bigger cabin and a well-deck like bay that can hold a pair of rigid inflatable raiding craft and their operators. A rear opening garage-like door would allow for deployment and recovery of these craft with relative ease and without compromising the boat's stealth capabilities for more than a short period of time. Additionally, the Sealion would feature state of the art electronics including a retractable FLIR turret, communications array and radar, along with a highly automated command and control system.

Another aspect of the Sealion program was to apply semi-submersible design philosophy to a high-speed special operations craft that could ride smoother through the water, as during heavy sea states injuries from hard slamming deep-v hulled boats and rigid inflatables had become a real issue within the SEAL community. Also, being able to sneak up on a moving target, such as a large ship, without showing up on its radar would clearly offer a huge advantage over boats normally used for missions which do not feature a high degree of "low observable" technology.

In the end the design would measure some 71 feet, feature an extremely small draft, would require a crew of one or two sailors to operate and would be capable of 40 knots under normal conditions and no less than 30 knots in sea states as high as level five.

Unmasking The Columbia River's Mysterious Stealth Boats

Although the original $9M Sealion was delivered in 2003 as a technology demonstrator and test-bed, with no stated plans to put the boat into production or operations, this seems to have changed as Sealion was quickly followed by a slightly more advanced Sealion 2.

Sealion 2 appears to be just a refinement of the original Sealion's design, is is said to be powered by a cutting edge AuraGen Viper 16,000 watt Marine Power system and is rumored to offer an even lower radar cross section than its predecessor along with requiring just a single crewman to operate it. But what is most telling about Sealion 2 is that Oregon Iron Works seems to keep building them and the US Navy seems to keep operating them, as evidenced by new boats appearing on the Columbia year after year. This realization also lends some credence to the notion that these boats may have become at least semi-operational in small numbers with the US Navy, or maybe some other nation's naval forces.http://www.reuters.com/article/2008/0...

Unmasking The Columbia River's Mysterious Stealth Boats

There are some strong advantages to the Sealion 2 concept over other swimmer delivery and special forces reconnaissance vehicle options. First off, the Sealion is certainly less expensive to procure and operate than an ultra customized and complex submersible swimmer delivery vehicle, not to mention the cost of tasking a nuclear submarine to act as their mothership.

Secondly, the Sealion can even work as a mothership for rubber raiding craft. This means this relatively inexpensive craft can enable a waterborne assault team all the way to its "last tactical mile," instead of relying on other craft for help, even in impermissible territory. Also, the Sealions are fast, with the ability to race towards or away from their objectives when stealth is not a huge issue, or they can lower themselves to just above the waterline to sneak into low and medium threat environments undetected. That is a lot of capability that covers a lot of missions in just one boat.

Theoretically, the Sealion could conduct shallow water patrol duties one day and clandestine surveillance or insertion missions the next.

Unmasking The Columbia River's Mysterious Stealth Boats

The Sealion Program is currently ran by the Future Concepts and Surface Ship Design Group and operated by Naval Special Wafare Group 4 located at Naval Amphibious Base Little Creek in Virginia. The boats themselves are operated by Special Warfare Combatant-craft Crewman (SWCC), the waterborne equivalent to the Army's famed 160th SOAR helicopter force.

The Sealion, and its Alligator progenitor, are by no means the only semi-submersible tactical watercraft sailing around the world's muddy littoral regions. North Korea is notorious for their increasingly technologically advanced semi-submersible boats, and this same technology has become an all-out favorite method of smuggling drugs into the US from South America.

Additionally, Iran has taken a keen interest in semi-submersibles and are fielding more of them each year. Swarms of these hard to detect boats could wreak havoc in the waters of the Persian Gulf and may even be able to clandestinely lay mines.

Unmasking The Columbia River's Mysterious Stealth Boats

The fact that some less than desirable people are using similar semi-submersible concepts may also give the Alligator and its bigger brother further utility as aggressor or adversary threat simulators. In other words, by having a similar, if not exceedingly more advanced technology as our potential enemies possess, US forces can innovate new ways to detect and engage these stealthy boats and train to do so using those techniques.

Although the program may not be secret, and it once kept a much lower profile than it does today, the Sealions sure do turn heads when they are spotted during the day. At least one of the boats seems to spend a lot of time down in Florida and has been known to temporarily dock at local yacht clubs between missions. Even boaters who have spotted a Sealion visually as it is semi-submerged say that it does not show up on their commercial grade radars, which is at least some proof to the Sealion's cloaking capabilities.

As far as I can tell Sealion remains just a Navy program and it is totally unclear just how much Israel still has to do with the program, if they have anything to do with it at all. Yet it very well could be that one nation's technology demonstrator is another nation's operational clandestine multi-role frog-man chariot of sorts.

As we wait for more details to emerge about exactly what Sealion is up to we will just have to keep watching the Columbia River closely to see what the Oregon Iron Works and the US Navy have up their sleeve next...

Unmasking The Columbia River's Mysterious Stealth Boats

A huge thanks to great friend of site Paul Carter for all the Columbia River shots of the Alligator and the Sealion. Make sure to check out all of Paul's aviation photography work here. Other photo credits: FLIR/drug runner image- Colombian Navy, camo Sealion going fast- Oregon Iron Works. Guests standing on Sealion- US Navy

Tyler Rogoway is a defense journalist and photographer that maintains the website Foxtrot Alpha for Jalopnik.com You can reach Tyler with story ideas or direct comments regarding this or any other defense topic via the email address Tyler@Jalopnik.com