Hunting practice or hunting failure?

I came across this scene at the pond on the way usual walking path.

A juvenile goshawk born in the forest of a golf club 2 km apart from here, the other day rushed into the flock of green-winged teal in a pond, but let the flock getaway

After that, it can't be helped, the juvenile pounced a night heron near being on the shore.

This doesn't look like serious hunting.

(the distance between camera and target is 70 meters, took with a hand-held.)

The juvenile catches the night heron's head with its claws and submerges it in water to suffocate it.

It seems to look like the night heron was stronger than the juvenile goshawk. 

The juvenile seems to have given up on capture.

                                       Relieved!

The juvenile drying down feathers wet with a large tree.