Doing what I want?

Currently, I'm on the first co-op quest where you go to the beach and spawn a huge ass dude to fight with a group. However, it was around this point that I decided that I wanted to just explore and do my own thing. Is there anything in the quest line that I should finish before doing so? I'm interested in fishing, but I haven't seen a hint or idea of where I can follow up to start doing so.

I've always read of the emergent gameplay from games such as Ultima Online, and I'm curious if I'm at a point in the quest line where I'm not limited to the story.