If you have happened to watch the movie
Mokpo Harbour, then I hope you haven't gotten the wrong idea on Mokpo city. The movie portrays Mokpo as an organised crime city of Korea.
Mokpo city is quite slow compared to the other cities of Korea. It does have good train services connecting to Seoul however. If you need to be near the water, then this is the place for you.
Mokpo used to be one of the biggest and best cities in South Korea. However, once the Japanese pulled out in the late 1970's, things started to take a steady decline. It is now one of the smallest cities in South Korea. But obviously big does not mean beautiful. All depends on what you are after.
Am sure you have already come across this site too:
Welcome to Mokpo City