What a difference the three years separating ATOMIC SUBMARINE and VOYAGE TO THE BOTTOM OF THE SEA made! Of course, Allen's much larger budget sure helped too. Still, one can see The Tigershark as being the direct parent of The Seaview.
We have an advanced nuclear sub capable of firing missiles or torpedoes and equipped with a secondary submarine. The Seaview originally carried a small fleet of 2-man submersibles but they got eclipsed by the flashier Flying Sub. And of course you have the senior officer, the younger guy who actually handles the action scenes, and a couple onboard scientists just for the heck of it.
The plot itself is pretty much the model for many of the Voyages to the Bottom of the Sea. The hidden mystery at the heart of an otherwise normal mission, the unexpected monster.... Yeah, this could have been a VOYAGE episode. And in fact, eventually IT WAS! VOYAGE did an episode that adapted ATOMIC SUBMARINE pretty much straight, just changing the sub, the crew names, and a few details (and ditching Joi Lansing's character, alas!).
While ATOMIC SUBMARINE does look frightfully low budget compared to VOYAGE, let alone today's super-bloated budget busters, it works pretty well for a product of its time. And the minimalist, barely illuminated alien saucer interior is surprising effect. I know it creeped me out when I first saw this late one night in '66!
