As well as having a healthy array of charms immediately noticeable and close to hand, Busan & Korea as a whole also has some lesser discovered awesomeness. There are still a whole heap of activities available in Korea that have not yet bridged the gap and become accessible to the international community. One of the more recent activities to bridge this gap is SCUBA diving.
Mention SCUBA diving to most people in the area and they look at you as if you are in some way deranged. The issue here is not the lack of diving potential but more the fact that this activity is vastly unknown.