HMHS Britannic, which sank in 1916 off the Greek coast likely by a mine, could become an underwater diving park. It has been declared a war grave and the Greek government has made it difficult to get permits to dive to it even for legitimate research purposes. That appears to have changed. The Greek economy is not doing well and there is a serious effort underway to make it an historical attraction with museum, hotel, and diving school. Unlike Titanic, there is not likely to be any salvage and would be treated as a historical exhibition you can dive to.
Source: Could the wreck of Titanic’s sister ship help save Greece’s sinking economy? (Daily Telegraph,18 Oct 2016)
World War I: HMHS Britannic (militaryhistory.about.com)