The Alpha might float around for several months - other boats have - and fetch up somewhere. But probably, it accomplished sinking without any help at all.

The comparison with the Lagoons was simply that they are claimed (nay, Certified!) unsinkable with multiple watertight compartments, and sank. I didn't say the Alpha wouldn't have more laminate than my boat, but it is unlikely to have more that twice as much, and it would need substantially more than twice as much for flotation. Nida Core is mostly air but so is structural foam. The densities are similar: Nida Core is 5 lbs/cu ft, most of my boat used 5 lb Core cell.

My point about sinking to eliminate the navigational hazard was actually a bit tongue-in-cheek: I don't think an uncommanded sailboat floating around adrift represents much of a hazard to most anyone. Certainly not a ship which would not even notice the collision, and if small pleasure boats run them down that speaks more to their watch keeping than unmarked hazards. It would be worse, certainly, if it was awash but not sunk - but still not a substantial hazard.