This could have made for quite a fun adventure, had the casting not been so terribly wooden! Four folks in a diving bell find them selves stranded in a network of caves. With now ay back to their colleagues on the surface, they must try to find a way out through the caverns - where they encounter their own equivalent of "Ben Gunn" (Maurice Bernard) who has already been down there for fourteen years. Meantime, topside, "Prof Wyman" (John Carradine) desperately tries to find a way to rescue them - but with the diving bell lost, can he find a way? There is a heck of a lot of back-projection and papier-mâché here. Not that that is so unusual, it's just that the cavernous scenarios and the really drab lighting make the film really quite dour to watch. It looks cheap! The dialogue and cast are just as mediocre, none of them stand out and the characterisations do tend to stereotype when things get perilous. If there was a budget, it went on the coffee - and I am afraid this is just not very good, interesting or captivating and you can spot the (magnified) archive footage a mile away.