In the central Pacific off the coast of Japan and areas near there, there are a large number of ships that sunk in this part of the ocean because of World War II. As a matter of fact, after battling in 1944 over the course of three days, at least sixty warships and two hundred aircraft sunk.
This created probably the largest graveyard of ships in the Pacific Ocean. I would say that the area of any ocean with the largest amount of ship graveyards would be those that had battles occur in that parts of the ocean during major wars. This is just one account where this occurred. This site is called Chuuk Lagoon and used to be called Truk Lagoon.