Jules Verne would be envious:

Voyage to the Bottom of the Sea features a submarine the length of two football playing fields.

Science fiction has a way of becoming fact and it would not be at all surprising if the sleek, fantastic summary that has the main role in the series should end up a blueprint on the desks of NATO. This extraordinary underwater craft with gadgets, chases about the watery depths after [marine life] twice as big as life.

It is all great fun. This hour-long adventure series is also fascinating because of the extraordinary submarine in which tight-lipped naval personnel patrol the ocean’s hidden depths.

Here are some vital statistics on submarine Seaview. It is 600 feet long, or the length of two football fields laid end to end.  In order that this remark with craft should remain hidden from the prying eyes of an unseen enemy and their nuclear detonations, a subterranean berth had to be made which could be reached by underwater sea lanes and on land by using a 200 foot deep elevator.

There are actually five Seaview submarines used in the series.

These range from the full-scale model containing the three main rooms, to an authentic  scale model, precision built to take the buffeting required for miniature and trick photography.

Fox Press Release

June 20, 1966