The point of the parable is, of course, that the fishermen weren't learning anything about the Sea, they were only seeing the effects of their net. Small fish escaped the net, leaving the larger fish for the fishermen's study.
In my interpretation of the parable, the world we live in is the Sea. It's unfathomable, mysterious, bigger than we can comprehend. In order to think about it at all, we have to cut it down to a size we can deal with. And so we fish out a few events to pay attention to. The contents of the net are the events that reach our attention. The parable is telling us that we shouldn't let ourselves forget about the existence of the net, or draw conclusions about the world as if the few events that grab our attention were the whole world.
My goal in writing the questions was to make our "nets" visible. When someone who thinks the world is getting better argues with someone who thinks the world is getting worse (Question 5), you very quickly realize that these two people are paying attention to very different events. If they listen to each other with patience and compassion, each may come to realize that his or her position on this issue isn't a conclusion, it's an assumption that shapes how he/she interprets the world.
Each of the questions has the potential to show us a way in which our assumptions shape our experience. To a very large extent, our assumptions make us the people we are. Seeing our "nets" can be the first step in a process of deciding what kind of people we want to be.