The food chain is real. Just because something is cute that does not mean it is safe from nature.
That is what we see here a mother duck and her family are swimming along and have no idea death lurks below. A decent-sized pike slow swims through the water and when in the unfortunate baby duck swims too close it strikes with lightning speed. The mother duck tries to save it but is too late.
If you have ever had a monster pike on the line you know how powerful they can strike. They are ferocious predators that will go after just about anything.
My brother witnessed one taking down a small muskrat while he was fishing, too bad he did not have the camera rolling.