yangtze river cruises

hi my fiancee and i if in god's grace will make it to hongkong we will get married in there hopefully and we want to have our honeymoon in a cruise ship tour to yangtze river because he really likes to see the three gorges dam i wanna know if its ok to take the tour from hongkong without a visa or if ever really need to have a visa to take the tour where can we process it and how long and if can we do it in hongkong?