Fantastic movie -- pre "Star Wars" and "Jaws", these disaster movies were as good as it got for thrills and special effects for 10 year old kids (which I was delighted to hear Ronald Neame say on the audio commentary track that these kids were their main target demographic, which is probably why so many people in their 50s love the picture so much)
And that cast -- all wonderful, great actors, many very familiar to kids watching a few of them in tv reruns on a daily basis (my idol Ernest Borgnine, yelling his head off Monday to Friday on "McHale's Navy" especially)
Many interesting things about this movie that may have made it even more kid friendly than the producers and scriptwriters realized -- the movie has only one villain ("Mr. Linarcos" played by Fred Sadoff, rushing the old ship to the wrecking crew in Athens, ordering stoic captain Leslie Neilsen to not take on ballast and go "full ahead") -- also, the entire screenplay (by Sterling Silliphant and Wendell Mayes) is made up of continuous one-liners from everyone (except Fred Sadoff) that kept the kids in the theatre laughing throughout -- a couple toilet gags (involving actual toilets, upright and upside down), fat jokes, scenery chewing by nearly the entire cast kept the 6 track stereo blasting away -- nobody could ever fall asleep during this movie.
This movie played here in Melbourne at Hoyts Cinema Centre in 70mm for 14 months and returned the following year (in 70mm) on a double bill with "Butch Cassidy and the Sundance Kid" for another month and a half. ("The Towering Inferno" was by then playing up the street, also in 70mm and ended up playing 13 months, ending its season in the middle of the box office success of "Jaws" in early 1976)