Thanks for reaching out on the esri community page. Have you already visually inspected the Senitinel-2 images? Is the water clarity good enough to make out features underwater? Do you have any known depth locations within the AOI? If the clarity is good and have known depths then you use empirical method comparing index of log ratio of blue band/ green band color at known locations.
the UKHO and NOAA have many old nautical charts available to gather some soundings in your AOI.
