I've seen something similar in the past. It was flooring, and a rather large boat came off it's mooring, and started floating down the river. We had a smaller boat, and were worried that it's chain would snap too, so we just happened to be out on the water while this was going on. So pretty quickly, the SES gets called out, but it will take them time to get that far down the river in these floods, and we offer assistance. They ask us to follow the boat and only act if somebodies life is in danger, otherwise don't touch the thing. So were in this small motor boat, following this yacht down the river, and all it going well when the SES guys turn up, and they are damn good at what they do, go the boat tred and started toeing it, the problem was they had nowhere to put it. So they decide to ground it in the soft mangroves, and tie it off to a tree. Nobody is in danger, minimal property damage!
However, you must remember that the river was flooring. Millions of insects, lizards and spiders live in these mangroves, and they are getting desperate for somewhere to stand as the water rises. Suddenly, big white thing that floats to stand on, yay! Within minutes, every critter than can reach this boat is crawling on it, and it was scary. I'm talking more critter than boat here, they were crawling over each other to get up. You have never seen more creepy crawlies in your life.
Moral of the story? Floors make small animals form mass swarms...