Help solve this mystery

Wednesday when on the beach in Garajau, I saw something floating out at the sea, I made Nelio go see what it was, I’m not a great swimmer… ? ?

This is what we found, it’s obviously been at sea for some time, anyone recognise what fruit, vegetable or plant pod this could be, it has a small pebble glued, and a piece of bone or something not 100%, sure. On the sail it looks like it had something written, but almost impossible to see what it was now.

Click the images below to open.