Some octopi species use halved coconut shells as a form of portable shelter! They can carry the shells with them for significant distances, ready to hide within when danger arises. This is a great example of invertebrate intelligence.
https://www.youtube.com/watch?v=RUN6c5yWJhQ
https://www.cell.com/current-biology/pdf/S0960-9822(09)01914-9.pdf