Really cool. Almost got bored and quit early from being repetitive, but then bought the first line upgrade and had fun exploring. A couple of things:
Do the fish not respawn? I upgraded my engine and bag and then couldn't find enough fish to upgrade my line further. Would have spent my money differently and wasn't as much fun trying to find every single fish in the ocean.
Would be cool if there was a "town" or something. Maybe like Harvest Moon where you try to catch as many fish as you can for the day then go into town and interact with people. Something to break up the endless fishing would be good I think.