Article here.
An octopus that uses coconut shells as portable armor is the latest addition to a growing list of animals that use tools.

The veined octopus (Amphioctopus marginatus) apparently can stack discarded coconut shell halves just as one might pile bowls, sits atop them, makes its eight arms rigid like stilts, and then moves the entire heap across the seafloor. These soft-bodied creatures perform this ungainly "stilt walking" to use the hard shells for shelter later when needed.

The discovery was a lucky accident.

More in the article.

I found it interesting.