In Palm Beach we dive on wrecks in strong currents. One thing we do is pretty much never use an anchor line. We drift into a wreck, make our way down stream along it and when we are done, we generally use a reel to send up a marker and then we drift off the wreck ascending slowly as we wind in the string on the reel.
On some of the deeper wrecks, I generally try to be drop 0.15 to 0.12 MILES upstream of the wreck (for 80 feet deep maybe 4- 500 feet away). This only works if the visibility is good and the divers can do drift dives, but it makes it much less stressful.
Also the comment about a hand hold is important too, You can hold with one finger against a strong current, especially if you get your chest low to the wreck and always keep your head pointing into the current if you are trying to cross it or oppose it. Sounds obvious, but people don't know this. Birds always face the wind, divers when stopped on a wreck need to act similarly
Another thing mentioned was don't try to fight the current too much. Watch the fish, they tend to know where the eddies are and the current can push you backwards on a wreck in some situations. Also if you are fighting a current to get a short distance do NOT go too slow! If you get into a current and swim just a tiny bit faster than it, you are getting nowhere.. getting more and more tired, wasting time and air. If you have good fins and are aerobically fit... shoot across the high current areas. Bust ass for 20-30 seconds and swim at maybe an 80% maximum effort, then hold on and rest. This is quicker and easier, then trying to plod along fighting a current.
This video I shot of my 13 yr old son and I and a few others diving on a wreck in probably a 1 kt current might give you ideas. We hold on, use the wreck for shelter, go inside where there is no current and if you skip to like 5 minutes you can see us leaving the sheltered inside of the wreck and then having to fight our way back into the current. I sprint ahead into the current and hold on and then film my son.. he SPRINTS for 8-10 seconds to fight the strong current in an exposed section and then immediately stops, grabs on and rests. Freedive fins are also extremely useful
[video=youtube_share;MvBdEb21UjU]http://youtu.be/MvBdEb21UjU[/video]