Well, to be fair, it's suspiciously close in time to the recent US/UK/France permission to use long-range missiles against the Russian territory. So it may be indeed a transparent hint towards them from Russia regarding how asymmetric response could look like.
Source, I was a diver in their north sea for some time. These expedition / treasure hunting vessels are common. They are definately operating as low key and under the radar as possible, for other reasons, but they aren't "spy ships'. There is no stealth ship that exists and can't be detected on the surface. The US military learned this the hard way with the Zumwalt Destroyers. If Russia is sabatoging undersea cables, as the daily mail suggests, they aren't doing it with "spy ships". Please get a hold of yourself and stop reading the daily mail.
