According to some dude calling himself “RAD”:
How do you define tool use? I came across the little octopus on a night dive. He was walking around carrying two halves of a shell with him. When threatened, he closed himself up inside the shell. Now many animals, like the hermit crab, adopt a shell for protection but in this case the octopus carried around two sides that he knew fit together. That comes close to tool use in my book.
We can no longer be sure what’s going to spring out of any given seashell. That’s terrific and terrifying all at once.