We know them in English as the Sea of Japan, the Baltic Sea, the East China Sea, and the South China Sea. But these names are contested, as this silly post at the Duck of Minerva shows.
In Korean, the Sea of Japan is the East Sea (Donghae).
In Vietnamese, the South China Sea is the East Sea (Biển Đông).
In Chinese, the East China Sea is the East Sea (Dōng Hǎi).
In German, the Baltic Sea is the East Sea (Ostsee).
I will not comment on the fact that Korean and Vietnamese use Chinese loanwords for “east” in describing the bodies of water that they wish to designate with reference to their geographic position relative to Korea and Vietnam. Oops, just did.