Before synthetic sponges existed, people used real sea sponges harvested from the ocean, and they were so valuable in ancient times that sponge diving became a dangerous profession. In places like the Mediterranean, divers would go deep underwater without modern gear or oxygen tanks, sometimes only holding their breath, just to collect sponges from the seafloor.
Even more surprising, during some ancient wars, natural sponges were also used as medical tools to clean wounds, long before antiseptics existed.
So that “simple cleaning sponge” in your kitchen actually has a history tied to deep-sea diving and early medicine.