The Drive has an excellent report on the sea drone attack on Russian Tanker Sig, including photos of the damage.
Looking at the video above, it is apparent that it starts with the unmanned surface vessel alongside ship or structure which might have been a point of reference. It makes a sharp high-speed turn until about time 0:19, when the target came clearly into view at a relatively short distance. This is a 37 second video, assuming 40 knots the UAS could go 4,000 yards in three minutes or only about 822 yards in the 37 seconds. The last 18 seconds when the UAS is pointed at the target would be a distance of about 400 yards.
The post also notes that Ukraine has declared six Russian Black Sea ports subject to “War-Risk.”
Chuck Hill's CG Blog 
I don’t know about this. 40kts is slow. The target is large. More a question of procedures to deal with it surely? I think it is being hyped by the West’s MSM due to the Ukrainian’s dire situation.
Now if it paddled in to a few hundred yards off to launch a small torpedo a different matter perhaps.
It seems the Ukrainians are locating the soft unwatched targets. Plus, the targets have all been lighted up making targeting easier. If detected early, .50 cal. and 14.5mm machine guns seem to have been adequate to deal with the threat. These last two incidents we saw no fire from the target vessels.
25 and 30mm guns in remote weapons stations with good optics should be very effective against this type of threat but remember, all those USNS ships run around completely unarmed.
I wonder about the beginning of the video too, but from a tactical perspective. I’m not sure where the video starts has a connection to a launch point, BUT it may…. Obviously, the location of the attack combined with the fuel range of these drone boats, means the attack was launched from occupied territory (which raises even more difficult questions) or from a “mother ship” which is capable of blending-in with commercial traffic, especially during daylight within RU shipping lanes. I find it hard to believe RU Intel cannot track every vessel in the shipping routes and do some snooping and evidence gathering to ID the mother ship…?
My presumption is that the devices are given a course to steer though a series of waypoints and only when it gets to the general target area does the operator take full time control to select and close the target. The operator certainly could have had direct control well before the video starts but the abrupt change of course suggests perhaps that was the point where the operator started looking for targets.
I do think it is possible that the vessels are launched from outside Russian occupied territory.
On the other hand, vessels transiting from Romania to Georgia could make the transit much shorter. I would think Russian surveillance would be most comprehensive in the waters West of Crimea. That area could be avoided that way.
Well, I did some research. These drone boats (not the Jet-Ski ones, but the jet-boat style, which is all I have seen videos of in action on Black Sea) are close, possibly a little larger than a Scarab 165. They also carry heavier loads (1000-lb warhead vs. Scarab’s 750-lb limit). Without setting aside space for a helm and seats, there is a lot of flexibility to add more fuel tanks too. Satellite uplink and remote control system weighs an insignificant amount.
The Scarab 165 comes with a 20-gallon fuel tank and has a range of about 175 km. Replace the seating area with a 150-gallon fuel tank, even with the heavier weights involved, I think they could get anywhere on the Black Sea without a mother ship.
Getting all the way to the East end of the Black Sea would still need some sophisticated planning, as some of the transit is going to be during daylight, and the drones are crossing three heavily trafficked shipping lanes, as well as close to the base at Sevastopol. Of course it depends on how much air surveillance the Russians are (not) doing too. The West has Reapers, Global Hawks, RC-135, RC-130s, and P-3/P-8s over the Black Sea regularly, but the Russians??
There is kind of a parallel with the low profile vessels used to smuggle drugs in the Eastern Pacific. They are larger and typically have a crew of three but they are very hard to spot, carry heavy loads, and they go great distances.
That’s true! The Ukrainian drones are painted black/Navy Blue too, so that will blend in well during the day and totally disappear at night.
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Russian SES missile boat being towed in. Looks like Ukrainian UAS was probably destroyed before it reached its target, but was close enough to cause significant damage. https://www.msn.com/en-us/news/world/images-of-russian-samum-ship-being-towed-are-published-on-internet/ar-AA1gOgYz?ocid=msedgntp&cvid=4f4121a356a94dd8bc5f03f653005eec&ei=17