From  your pics, looks like he tried to do the easy thing, pull in bow first, just tie off, then head for cover.

The easy things the wrong thing.  Had he tied off right, he'd still have a boat not a sub.  

That exact thing is against the law in TN at a public dock, a $650 fine, its basically blocking the dock.

About 14 years ago, I was trying, me and a dozen other boats, to beat a bad storm to the ramp.  Easy guy had tied his boat off by the bow, ran for cover, and while him and his buddy stood under a tree, his boat swung side to side blocking the entire dock and ramp. We're stacking up as boat after boat lines behind us, the wind is crazy, raining like hell, and lightening hitting the water.

I hail the guy to secure his boat, "Tie it off".  He just laughs and shoots me the finger. Here he is out of the weather, watching dozens of people get soaked, women and children in danger of lightening strike many in open metal boats, breaking the damn law, and not giving a damn.  He thinks its funny.   I yell back, "Secure the damn thing or I'll blow a hole in your hull the size of your fist and if I can't go around your boat, I'll go over it."  

(I was serious as hell too.  I would have put two barrels of "OO" through his hull faster than he could think.)

He ran for his boat.  All the butthole had to do was tie off aft, one line.  Looks like all your genius had to do was tie off one line aft. Instead he got a bow under a dock, the boat couldn't rise with the waves, and down he went.  He's got a bit more to do now.

Tell you how cynical I am, I bet in their hurry him and his crew just walked right off that bow pushing it under the dock them self.    

Me, I'm happy as a lark for the last ten years I've been in a Marina slip and only have to deal with idiots on the water.  

Remind me to tell you some of my tow stories, people I have rescued.  I have some doozies.  Idiots come in all size boats.

Tj