Giant Octopus (MA)

The Giant Octopus 大ダコ (Oodako) of the Planet of the Monsters continuity is a giant octopus-like created by  that first appeared in Godzilla: Monster Apocalypse, a prequel novelization for the 2017 film, Godzilla: Planet of the Monsters.

Godzilla: Monster Apocalypse
It inhabited the Pacific ocean and had been attacking and sinking fishery vessels and transporting ships two or three times per year.

The timing of its activities was possibly before appearance of Godzilla, as it was said that Godzilla declared the Pacific ocean as its territory, and not only other monsters were scared off of Godzilla, but also corpses of monsters had been confirmed occasionally since after Godzilla appeared. It's not clear whether Giant Octopus was one of those.

List of appearances

 * Godzilla: Monster Apocalypse