He was shot down in the Pacific Ocean in WWII. Almost 80 years later, his remains are finally home
https://edition.cnn.com/2023/07/08/us/new-jersey-world-war-ii-soldier-remains/index.html
Something sunk in the ocean is usually preserved in good situation. That's because it's away from criminals who want to steal it, and oxidation of it is mitigated by surrounding water.