There is not a good way to legally watch "Rescue from Gilligan's Island" online, as of 2015. The main online streaming sites, such as Netflix.com and Amazon.com, do not offer a streaming version of the movie. However, the video is available for purchase from many online retailers such as Amazon.com.
The reunion movie first aired October 14, 1978, and the T.V. series aired from 1964-1967. Warner Brothers began efforts to remake "Rescue from Gilligan's Island" in 2013 but was subsequently sued by a Georgia man in August of 2014. Travis Dunson claimed that he wrote an adaptation in 1999 titled "Gilligan's Island: 7 Stranded Castaways From the Hood," and that Warner Brothers expanded on his original idea.