That's very cool!
Also, since you said you put them back to the sea, I wondered why should you do that? I googled and found out that corals are ALIVE! Omg, I always thought that they are just sea-rocks. No harm has ever done to any corals though. :D So, that's a new knowledge for me. Thank you for that. :D
Thanks @liberviarum! I collect them from the shore, take a photo and put them back to the ocean. I have never looked at corals the same way since I started doing this. 😂 I'm always on the lookout for letters. I'll try numbers and shapes next time. 😊
Yes, coral is alive! Unfortunately is dying in all oceans...you should check the documentary "Chasing Coral" and you will realize what is going on :)