Go Qingdao By Boat

Incheon
From Incheon, Korea there are ferries three times a week by Weidong Ferries.

Shimonoseki
There are also twice-weekly connections from Shimonoseki, Japan on Orient Ferries. The trip takes over 24 hours and 2nd class one-way costs ¥12,000. The voyage is one night from Shimonoseki to Qingdao, but two nights from Qingdao to Shimonoseki. The ferry also serves as a cargo vessel and after boarding in Qingdao, it will often take several hours to finish being loaded with cargo before it departs.

The restaurant food and drinks, snacks and souvenirs from the shop are all priced in Japanese Yen, so make sure to get some/have some left over before boarding. The cost of most food and drink is reasonable considering you're stuck on the boat with nowhere else to buy things, but the pennywise traveler will definitely bring their own alcohol, cigarettes, and snacks. (mind that there might be duties when crossing into Japan or China).

There are electrical outlets in the lounge area, but if those are taken, there are also some up in the gym/fitness area, where no one goes. Be advised that on boarding from China, the ship operates under Japanese time, so change your watches and pay attention to announcements for when dinner will be served, as food is only served at certain times of the day. There are Japanese-style shower/bath rooms on the upper level where the first class rooms are located.

Quoted from http://wikitravel.org/en/Qingdao