On the level of the worst Disney and more like some 1930s action-adventure movie where, say, the guide yells "Look" and points left while the camera cuts to cheap stock footage of a lion running off to the right somewhere.
There is nothing - not one single thing - worth watching in this movie. Even Caine is bad.
The effects - one of the reasons one might watch something like this - are below anything you can imagine: a ship floats in the back on an ocean a different color from the "real" ocean in front; the octopus has one rubber tentacle that's dragged around in an aquarium.
But most - maybe 95% - of the movie is talk. Nemo shows folks around his sub for hours (or days or weeks); the hero lectures some scientists forever. it's just talk and more talk with an occasional shot of a metal sub model.
Avoid this at any cost. It's not even watchable over pizza when you're reading or doing something else; it's not even close to as good as the worst Godzilla movie; it's worse than "Plan 9" but without the camp.
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