Ebirah, Horror of the Deep (1966)

"The atrocious new monster Ebirah! Three giant monsters of the land, sea, and sky take part in the confrontation of the century!"

Searching for his brother, Ryota stows away on a boat belonging to a criminal alongside two other teenagers. The group shipwrecks on Letchi island and discover the Infant Island natives have been enslaved by a terrorist organization controlling a crustacean monster. Finding a sleeping Godzilla, they decide to awaken him to defeat the terrorists and liberate the natives.