Have you seen the "documentary" on a 35 foot long great white shark dubbed Submarine? It looked pretty good. Not like the Megalodon show, filmed like the Blair Witch Project, ie. really jumpy and obviously fake.
However, I think this disappearing buoy presents a problem.
The buoy: at least 4 feet in diameter and 10 feet long, to be conservative.
The volume is over 125 cubic feet. Water weighs 62.4 pounds per cubic foot. The force needed to drag this buoy under in distilled water is 7839 pounds. Sea water is denser and heavier than that.
So, the 35-foot shark needs a downward thrust of about 8000 pounds. If a shark could thrust that much, and that shark weighed 8000 pounds, twice what a normally huge great white weighs, then the shark could accelerate with 1 g.
That's like doing 0 to 60 in 2.74 seconds. Or 0 to 30 in 1.37 seconds. Some animals look that quick. Only a few super cars can do that. Many super bikes can.
But, to take the buoy under in one video frame? Let's give them the benefit of the doubt, and assume they only filmed with 15 frames per second. This minimizes the required power, speed and acceleration.
First, let's do speed. The buoy moves 4 feet in 1/15th of a second. The speed is 4 times 15, or 60 feet per second. That's equal to 41 mph. Hmmm.... That's really fast. The fastest shark is believed to be the mako that can sprint temporarily up to 60 mph. I think the blue whale can cruise at 30. Eh... maybe a humongous great white can go that fast.
Let's do acceleration. 0 to 4 feet per second instantly. Uhhh, that's an acceleration of infinity feet per second squared, approximately infinity G forces. Approximately.
What exactly did the shark grab onto? The narrator said the woman was attached to the buoy, and the shark was only pulling on the woman! Nonsense. So, her body pulled the rope, which in turn pulled the buoy? Not a chance.
And to take it down and never to be seen again? LOL
Plus, the splash and waves are much too small.
This documentary is fake. Shame on you, Discovery Channel and Animal Planet.