There was absolutly supposed to be a second ending, but I ran out of time, The one ending the game has now is some kind of ducktaped together hybrid of the 2 planned endings.
The attack option was supposed to let you kill the other guy with a few quick time events, and then you would throw him in the water. but, this was obviously way to ambitious and didn't make it in.
I hope that this didn't completly ruined your experience and I completly agree that the last options are kinda useless.
But I'm glad you enjoyed the first parts!