I am an archivist and a writer. Many years ago I had a flood at my home, and boxes and boxes of research were nearly lost. My friend Lisa Fox who was an archivist and handled the restoration lab for the Missouri State Archives told me what to do. Get the water-logged paper and photos into a freezer immediately. The freezing process not only stops the mold that begins to grow and damage the items but also draws the moisture out of it as it works as a dehydrator. I was able to salvage nearly everything! Except for a book on Daniel Boone, which had slick pages which became a solid brick.
When things calmed down, after all the hours hauling debris and carpets out and the walls were repaired, I went back to my items in our freezer. I would routinely take a folder or stack of pictures out and check their progress, rifle through them, and if almost dry lay them out on a flat surface that had good airflow. If it was an old Carte de Vista (those old family photos that are like on a piece of cardboard 5X7) it would take longer to become totally dried out. The freezer did all of the work. It could take a few months. Have patience.
As an archivist and a genealogy teacher, I always suggest this for the storage of photos. Digitize IN COLOR and print two B & W copies. Put the original in a plastic sleeve (not one that contains PPE) and on the B&W copies, put the names of the people. On the back, put the date if you know it and the location. Store one with the identifications with the original in the sleeve, and keep one for your use. Store all sleeves flat in a shirt box on the top shelf of your bedroom closet. Why there? It is dark, dry, and at a constant stable temperature, just what an archive needs. Of course, keep genealogy backed up from your computer on a thumb drive routinely. I keep my thumb drive on my car keys.
I do hope this helps anyone who has had flood damage save those most precious photos! It does work! Companies that do business restoration after floods will actually rent space at a butcher or other cold storage locker. Don’t let time go by! If you have a friend who has been flooded, you can help them a lot with a little space in your freezer!