Why are tattoos not allowed in Korean public pool?

I went on a business trip to Korea and stayed in a nice hotel in Seoul. When I went to the gym to use the pool. They warned me that you could not swim in the pool with any visible tattoos. Why is that? I have heard that in Japan they are concerned about tattoos designating you as Yakuza. Is it the same type of reason in Korea? Or, is there some other cultural issue.