When preparing your presentation for use on a cruise ship or a keynote or training etc, be careful as to where your source material comes from. US Copyright law gets revised periodically, and ignorance is no excuse in a courtroom. In summary, the public domain consists of ideas, facts, mathematical theories, history, and works with expired copyrights.
A work does not enter the public domain simply because it is accessible to the public online. A “work” has a copyright the moment it becomes fixed in a tangible medium of expression. The author of the work does not need to take any formal steps, such as registration, to receive a copyright. It is NOT necessary to put the © mark, although it will deter amateurs. It can’t hurt. Copyright is automatic, and thus a work cannot enter the public domain until its copyright has expired. Anything before 1922 is fair game – there was no law then!
The Copyright Act gives the owner of a copyrighted work five exclusive rights: (1) the right to reproduce the work; (2) the right to prepare derivative works; (3) the right to distribute the work; (4) the right to publicly perform the work; and (5) the right to publicly display the work.
My suggestion – be careful. You never know who “owns” the photo or words. They can sue you for big bucks. Attribution may help but is not legally binding. Check with your lawyer for an in depth discussion. Read this article for more information.