The bottles have been at the bottom of the sea for a century with the contents diffusing slowly out through the cork and the ocean salt water slowly diffusing in through the cork. Even though the diffusion process is slow it’s been going on for 100 years. I suspect that the contents will be more sea water than anything else.
Apparently the bottles had wax seals so it is possible that some are still good. Also, check out this article about storing wine at the bottom of the sea.
https://www.rt.com/russia/472632-cognac-russian-tsar-recovered/