Suncheon Bay Ecological Park is a great place to learn about how South Korea takes care of their environment. While walking through the wetlands (on a boardwalk), you can see crabs, birds, mudskippers, and other animals. Then, enjoy a hike up the mountain to watch the sunset over the bay. It is truly breathtaking.
There are shops selling handmade, organic products and a museum/observatory. All of this will only cost about $2 per adult. Can't beat it!
In order to get to the park, take bus 67 to Suncheonman. Taxis might be your best bet back into town, but they can be a bit pricey. Try going with another group. Everyone is trying to get to the town center at the end of the day, anyway.