I once owned this movie on VHS and while it's been many years since I've laid eyes on it, I remember it well - and that, for me, is generally the sign of a good movie. Some of the criticisms levelled by fellow armchair critics are valid (e.g.overlong) but it's still a very picturesque and curious movie that's definitely worth a look.
Douglas is fairly restrained as the sole survivor of a remote island lighthouse, besieged by pirates led by the pitiless Yul Brynner, his clan of bandits opportunistically decide to use the lighthouse to misdirect approaching ships into the rocks where they can pilfer the payloads. Samantha Eggar plays one such shipwrecked maiden taken as a romantic gesture by Brynner, and who Douglas (who's taken refuge in a subterranean cave with his pet monkey), must try and free.
Reasonably violent, though it's Jules Verne inspired, it's not the typical family fare you might expect. Little dialogue and a fairly loose plot might not convince some audiences, but overall I remember it to be quite a sombre picture, with a few cruel twists and a fiery conclusion. Great cast as well with support including Fernando Rey and the familiar faces of Aldo Sambrell, Victor Israel and American ex-pat in Spanish pictures, John Clark.