Nautilus Alternate Version I

looks more plausible than the Disney version, the ram made me think of the 19th century submarine built by the engineer Holland for the Irish Fenians in New York ~ sub was called the "Fenian Ram"

Note that you're from U.K. check out the novel by the Cornish writer Craig Weatherhill, a sequel to Jules Verne's The Mysterious Island which is called "Nautilus".  Hint the author came up with a plausible explaination of how the Nautilus works,