Quote Originally Posted by that_other_guy View Post
When the tractor went onto the back of the "ferry" and the front end of the ramp went up you can see one free buoyancy tank.
Then after it flips off, you see another extra one on the left side but free.

My guess is that those two tanks from underneath could not be inspected and were ready to come free.
Then when the tractor first hit the deck they both broke free, one went forward and out, the other back and left.
It left the platform unbalanced.
After the tractor is submerged, and the raft regains the upright position, you can see the transom of a boat beneath the deck that was added to provide additional flotation. When the tractor tips the raft, while attempting to mount, the boat tilts and fills with water, thus losing any flotation that it might have provided.