Peter Ericson’s review published on Letterboxd :
An old-fashioned, fairly entertaining fantasy-adventure movie with some beautiful underwater scenes and a great, rather imaginative set design. However, the film is largely predictable, sometimes silly, and not particularly engaging. The plot, while thin, occasionally nourishes the imagination. Uninspired direction by James Hill.
"Captain Nemo and the Underwater City" is generally well acted. Interesting dynamics between Robert Ryan as Captain Nemo and Chuck Connors as Senator Robert Fraser. Bill Fraser and Kenneth Connor are more annoying than funny in the roles of the comic-relief characters Barnaby Bath and Swallow Bath, respectively, but there is a nice, non-comical scene in which Swallow finally stands up to his brother.