Hey, I took a group out to China Creek a few years back to do both the wall and the chinese wreck (which was in bad shape even then). The marina has a main office with phone booths and such, and might be able to give you some more current info about the sites. They also have maps of the area in the office so you can see exactly where to go and park and etc. I wrote down the following after the dives:
China Creek, Wreck of the Rusty Boat that carried 130 people from China
See map of China Creek Marina. Swim straight out from campsite 42 to the small yellow marker buoy. This was a very small buoy barely visible once you were in the water. Clever compass work would be a benefit. If you cant find the buoy, head out a bit towards the wall (from campsite 44 or so) and swim to the right along the 80-85 ft contour. From the marker, descend down the line to meet the wreck at 60 ft. This is the stern of the ship, sandy bottom was at about 80ft. The wreck is 120 feet long. At the stern, the deck is approximately 110 ft deep and the boat easily hits sandy bottom at 150ft. Not much life and quite rusty.
China Creek Wall
China Creek wall is the rocky wall on the left-hand side of the photo below. Youll notice that from shore it goes wall less wallish- wall. Swim all the way out to the end of the second wall for some huge boot sponges and a fairly nice wall dive reminiscent of Ansell Point. Wall goes down to about 90ft, breaks into rocks before hitting the sand. This is a dive site for looking close at invertebrate life, and searching in crevices for things like juvenile wolf eels and grunt sculpin.
At 40 feet in the wall part closest to shore is a phone booth. Surface swim is long, shallows are pretty and water very clear. I heard that there is a tugboat somewhere also, although perhaps that was the second marker out from campsite 44ish.
There's also an interesting link to information about the Chinese wreck found here
http://www.library.ubc.ca/asian/FinalAsian/introduction.html
Hope that helps! If you dive the wreck, can you post an update on its condition and depths? I thought that it might perhaps be sliding down the slope it was on. Good luck with the sixgills too!