Wake of the Red Witch 1948

This being a Republic Production means that the miniature effects were handled by the Lydecker brothers Howard and Theodore. The special effects credits are sub-headed under-water sequences although there are some miniature surface shots of model ships as well. 

The bulk of the work is indeed in an underwater setting with a miniature shipwreck teetering on the edge of a precipice which eventually slides over the edge. There is also a marionetted diver figure with subtly moving arms and legs along with the emission of a stream of bubbles.

 

Hearts in Bondage 1936

Probably the Tora Tora Tora of its day in terms of the quantity and quality of model ship action, the movie tells the story of the meeting of the Merrimac and the Monitor, two iron clad ships that were the cutting edge of naval technology during the American civil war.

The miniature effects were supervised by Bud Thackeray with the other Republic Pictures effects staffers the Lydecker brothers (Howard and Theodore) also working on the project.