Classic public domain film, digitally preserved and free to stream forever.
20,000 Leagues Under the Sea (1916) is one of the first underwater sci-fi adventure films ever made, based on Jules Verne's classic novel. A naval vessel is sunk by what appears to be a sea monster, but survivors soon discover it is actually the submarine Nautilus, commanded by the mysterious and brilliant Captain Nemo.
Starring Allen Holubar, Jane Gail, and Curtis Benton. This film is in the public domain and free to watch, download, and share.