Text in hover box over thumbnail image

In my photo-blog I’m using the Spotless theme, which is a very clean style. But sometimes I would like to add a small paragraph of extra information (not Exif data) about the images. To keep the uncluttered design it would be helpful if that information could appear in a hover box when the cursor is placed over a specific image on the archive page.
The page is – https://www.coppercoastworkshops.com/minimalistics/archive.

Please would someone let me know if it is or isn’t a possibility – Thank you for your help.

Seoirse