I want to study segmentation and object recognition (specially mine-like-objects) in side-scan sonar images. I've downloaded several journals about these topics, but I couldn't find any relevant database.
Aside from some sample images (see https://www.edgetech.com/underwater-technology-gallery/ ) I couldn't locate a database either.
If you have an "official" project: try to get contact to some side scan sonar manufacturer (eg. Hummingbird - https://www.humminbird.com/freshwater/home/ ) and see whether they can help you - with some database or with appropriate contacts.