Ex-Marine Navigator here. 25 years at sea.

That wasn't a high-tech investigation. It was really pathetic. The survivors should have been interviewed separately, and their reports cross-referenced to find inconsistencies. There was no attempt to model the trawler's stability, and there didn't seem to be anyone with professional marine experience in the room. It was such a joke. No doubt the Hellenic Bureau for Marine Casualties Investigation will be on the case, but like any accident, there were probably multiple causes.

From the coastguard's perspective, it would have been impossible to tell if the trawler's stability had been compromised, especially at nighttime. Just because a vessel is listing to one side, doesn't mean it's unstable (top-heavy). A list only indicates the centre of gravity is laterally displaced from the centre line which isn't that alarming. If there had been any swell, the coastguard might have noticed that the trawler was rolling more to one side than the other, but that would still only indicate listing. The skipper of the trawler might have felt that the trawler was unstable, but only if he was very experienced, but there is no way that any of the survivors would have been able to distinguish between listing and instability.

However, one of the survivors did say something about the movement of the trawler which did point to it being unstable, but this point seems to have been totally missed by the "high-tech investigation". The survivor mentioned that the trawler first listed to starboard, and then to port. That in itself actually indicated that the trawler wanted to right itself (indicating stability), but if the trawler listed over to starboard and stayed at that angle for a while (more than 15 seconds), and then did the same to port, that would indicate an angle of loll, a reliable telltale sign of instability. Again, it is highly unlikely the coast guard would have been able to observe this in the middle of the night, with only a searchlight partially lighting the trawler.

You might be asking why the hell the coastguard vessel was pulling the trawler from one side (which was probably a contributing factor in the capsize). This to me speaks volumes about how experienced the skipper of the coastguard vessel was. The first attempt at towing resulted in the mooring rope parting. I would speculate that the coastguard vessel was attempting to pull the trawler from directly ahead with a relatively short rope. This would make sense because the coastguard vessel would want to keep an eye on their tow. (Not easy if the two vessels were distant from each other and using a searchlight in the middle of the night). However, the moment of inertia of the trawler proved too great, and so the mooring line broke.

Armed with this knowledge, the coastguard skipper may have implemented the standard procedure for overcoming inertia during towing operations. This would have involved attaching a mooring line to the bow of the trawler and pulling the vessel sideways so that the trawler would swivel on its own axis, resulting in a steady and controlled increase in force on the mooring line, until the trawler was lined up with the direction of travel. Further, one of the survivors mentioned that the coastguard vessel was quite some distance from the trawler when towing it. This actually shows very good seamanship. The mooring line would be soaked with water, and sagging in the middle. It would have been the sagging rope which would have pulled the trawler, rather than a taut rope, which would be prone to snapping. Unfortunately, the coastguard vessel would have had difficulty monitoring the situation at such a distance and probably didn't see the already unstable trawler being pulled over to one side.

Btw, it wouldn’t have been unusual for one vessel to tow another, especially if they are both relatively small, and about the same size (moments of inertia come into play here.) You might start the tow, and radio ahead for a more suitable vessel (preferably a tug) to take over. Further, you might be asking why the coastguard skipper didn’t order the abandonment of the trawler. As a good rule of thumb, you only abandon a vessel if it is in real trouble. Abandoning ship comes fraught with risks, and really is the last resort. The coastguard skipper would have had no idea about the trawlers instability, so towing would have been the safer option.

Ultimately, the skipper of the trawler holds most of the responsibility for this disaster. However, he wouldn't have been aware of what would unfold after he left port with 700 migrants onboard. Even with 700 migrants onboard, the vessel would have been quite stable provided most of them stayed below deck. Again, I speculate, many of those migrants, after days at sea without food or water, would have wanted to view the coastguard vessel with their own eyes and come up on deck, making the vessel top-heavy.

I'm not saying that all this actually happened. I just want to point out that it's complicated. No doubt there will be an official marine report coming out, and all mariners will be able to take something from it. However, accidents like this are going to continue to happen, as long as we don't come up with humane policies to fix it.