The Osprey was in water so therefore at a disadvantage. I think the Osprey might have been emerging with fish which can put them in a dangerous position.
check this picture out a gbb gulls caught and took down an osprey it was probably just trying to take its catch, I dont know if it drowned it or not. Just shows you the raptors easily get victimized.
The last one it caught a female p falcon
Last pictures show you the power of the osprey it is about to kill a blue heron it flipped iti n the air tossed it into the water was about to kill it but then it was saved by some wildlife people.