Sometimes your eyes are bigger than your stomach, that seems to be the case here since this snake can hardly fit this catfish in it's mouth.
Snakes are sometimes known for taking down prey larger than themselves. Usually when that happens, it's a big snake, and it has the ability to greatly expand it's jaws to accommodate it's newly captured meal. Sometimes though you run across something like this botched water snake who can hardly fit his meal in his mouth.
It looks like the predator eventually won out, or at least got the fish down completely underwater where he can continue to work on getting his supersized meal in his mouth. This whole video is an amazing display of how water snakes work in general and to always remember that in their eyes there may be no such thing as a meal too big.
Definitely something to keep in mind when you have small kids or dogs out in the wilderness near places where water snakes hang out. Even though the botched water snake is non-venomous, it's still not a battle you want your young ones fighting at the water's edge.