An SDV goes Gävle

So it seems that approximately once a year there is some kind of more serious unexplained underwater activity in Finnish or Swedish waters. On 29 June it was the port of Gävle’s turn to be at the centre of attention.

Following dredging works in the main sea lane leading into the port, a hydrographic survey was made. As is usually the case when measuring small areas where high precision is needed, a measuring frame was pulled under the water at the correct depth (for simplicity, think of a welded frame being pulled at a constant depth, indicating if it hits something). At the very inlet of the port this indicated some kind of “anomaly”, and it was decided to scan the plot with a multibeam sonar. The area was then scanned between 11:00 and noon, after which followed a lunch break during which the scans were studied closer. It was then that the crew thought that the shape looked “boat like”, and after lunch the area was rescanned around 13:00. The “anomaly” was still there, and the survey vessel ran a few laps around it. The vessel then went to get divers, and when the divers arrived around 14:00 the anomaly wasn’t visible on the multibeam sonar any longer.

The object is described as around 12 meters in length, and roughly 3 meters high.

It does seem clear that it was some kind of a underwater vehicle. It was observed by professionals, using proper equipment, and observed numerous times before disappearing. It should also be noted that the location meant that if it had been there for any longer periods of time, it would have been hit by a passing merchant vessel.

The obvious next question is what kind of a vessel it could have been. It does seem to feature a quite pronounced passenger bay, meaning that it is likely a ‘wet’ swimmer delivery vehicle, SDV, in which divers sit with their gear on, and not a ‘proper’ midget submarine. There are two (likely) operators of these in the Baltic Sea: Russia, and Sweden.

Russia (probably) uses the Triton-NN, which rose to fame during the Swedish sub-hunt a few years back when it featured heavily in the speculations. Here there’s the obvious point that Gävle was mentioned by Gerasimov in April as part of a staging area, as discussed on the blog earlier, and as such it is likely the target of some form of intelligence gathering efforts.

A more likely candidate, however, seems to be the Swedish JFD SEAL Carrier, which the company has confirmed it has delivered to the Swedish Defence Forces. The likely user is the combat divers Attackdykarna, thought within the Swedish Defence Forces there are also other potential operators under the surface, such as the special forces (SOG), underwater clearance teams (Röjdykare), and even certain army engineers practice diving.

Compare the general dimensions of the SEAL Carrier to the skiss above. The vessel is 10,5 m long, with a width of 2,21 m. The stern is sloping (tumblehome, left side of the picture), while the bow is more sharply built with the crew/passenger compartment being the open bay close to the bow. Perhaps the most significant feature is the round object to the left of the centreline just aft of the passenger compartment. This location matches the location of the snorkel on the SEAL Carrier. As it happens, the Triton NN is more or less an mirror-image of this design, with a car-like bow and a passenger-compartment towards the (straight) stern. There is also a snorkel mounted on the right-side in front of the passenger compartment, but the proportions doesn’t seem to match as well.

As such, my impression is that this is an example of the Swedish Navy’s combat divers being accidentally found during one of their unannounced exercises. As such, the outcome of the incident is probably not much worse than that someone has to buy someone else a round of drinks. Keep calm, and carry on!

Points to @covertshores, who I believe was the first one to point out the similarities to the SEAL Carrier.