Okay, so someone made a mistake on the tug. And a few people jumped overboard.
First of all, they shouldn't be there in the first place, it's the "dangerous" side of the tug. Now you see why.
But they were still swimming next to the tug, the captain flipped the tow-hook in the last second, preventing the tug to flip over.
Worst thing what happend there? 3 man or so had wet clothes and the engineroom has a bit to much water in it. No one drowned. And the tug still floats. This is not trgaic, it happens more then you think.
That's why the tow-hooks have a build-in safety. If things go wrong, the captain can pull a string, and the hook opens up.
However, when the captain panics, and forgets to flip the hook, the tug will flip over, and then it's tragic indeed.
Just my 2 cents.