Ebirah, Horror of the Deep (1966) directed by Jun Fukuda

Also called Godzilla vs. the Sea Monster, this is an odd Godzilla movie in that the human part f the plot isn't so boring or beside the point. Godzilla only appears at the end and Mothra appears after Godzilla. Ebirah is a giant lobster who only shows u now and then, killing anyone who tries to leave the island run by an evil terrorist organization called the Red bamboo.  There is also a giant condor that comes out of nowhere and doesn't last long. The Mpthra worshipping native of a nearby island are slaves fo teh red Bamboo who have them making a yelloe substance that can stop Ebirah from attacking boats so the terroists cane come and go as they please. 

OK the human story is not exactly plausible but the characters are fun and interesting enough to keep you interested. The effects are not gratifying, some of the model work is super but the lack of realism has a certain charm. Some shots of the tiny singers who call Mothra are just dolls and on some of the boat senes, the ment rowing or dolls or even articulate puppets. It's super obvious and, like I said, charming. 

The bad guys are killed by Ebirah while making their escape but they have set an atomic bomb to destroy the island before they fled and our heros become concerned that it will killed Godzilla who saved them. Why? Godzilla is usally living off nuclear energy and jumping into the water wouldn't save him so close to the explosion if it was a danger to him. Don't watch a Godzilla movie, aside form the forst Godzilla minus 1 if you are looking to make sense of it!