[LargoLasskhyfv]

Depends on the sort of water, I guess. Salty and oxygen-rich wouldn't be so good. I'll just leave the https://en.wikipedia.org/wiki/Antikythera_mechanism here for you to think about. That had ca. 2100 years +/-ca. 100 years of underwater seawater exposure, and look what it did to it.

What would only 10000 years more of that have done to it?

[nemo]

That's bronze. I'd assume any brass/bronze/copper to corrode away, that's what it does naturally. Now consider gold, stainless steel, and the many other inert materials humans work with. I assume 10,000 year old gold artifacts would look the same as the 5000 year old artifacts we know of which are very well preserved, and other similar materials would fare similarly.