I happened across this article in Nature: 'Constraints on global mean sea level during Pliocene warmth'.  It shows a nice vertical profile in part of the Coves d'Arta, Mallorca and a picture of a deep part labelled 'Infern' (Hell ?) and some speleothems which are interpreted in the article as indicating sea-levels at half a dozen times in the above time period.  They were able to date them by radioactive decay of uranium to lead, and to figure out that sea-level was 23.5 m (9.0 to 26.7 error bar) above present, at a time when CO2 is estimated to have been 450-475 ppm.
For me at least a fascinating side of sea-caves being relevant to current concerns. Of course it also indicates just how old some caves are.
https://doi.org/10.1038/s41586-019-1543-2