All for Nothing

I was in a medieval-style port city. I was looking for something, a way home. Walking along the stone docks, browsing the wares of foreign traders. When I notice a man beating a young woman. I walk up and stop the man rather violently. I tell the woman to get on a ship and leave (thinking I was doing the right thing). She grabs her belongings and boards a small vessel that is about to set sail. I sense a good feeling, a feeling of doind a good deed. That is up until a sea monster capsizes the ship, taking all inhabitants to the bottom of the sea. The man dissapeared and I had I horrible feeling of regret. Like my actions didn't do anything to benefit anyone.

Can anyone interpret this dream for me? Maybe just try?

Information: I'm Male and 17. I've never been exposed to violence against women. With the exceptions of late night arguments between my parents that never became violent. That was years ago, now.