Why can't the submerged ruins off the coast of Japan be radiocarbon dated?

Question

not those kinds of ruins...it's archeological, it's just weird because they can radiocarbon date rocks and what not, but not stone ruins

Answer 1

The object being dated must have carbon-14 in it; a metal ship doesn't have any carbon in it. Only organic compounds will contain carbon

Answer 2

They don't radiocarbon date rocks. Different methods (like Potassium/Argon and Uranium/Lead) are used to date minerals.

Even if these were used on the submerged ruins (or any other archaeological remains) - it would just date the rocks themselves, which were obviously formed a long time before they were quarried and used to construct buildings. It does not provide any information on the time of construction.

Generally, other remains found near the site of such ruins can be used: old food remains, clothing, etc. that is found by archaeologists when excavating the site. Radiocarbon dating IS used for these things.

Being submerged, however, will have destroyed any such remains at the Japanese site, so radiodating to find the age of the ruins is not possible.