Which of the following items is NOT commonly collected by divers?

The item that is not commonly collected by divers is trash. While divers are often encouraged to engage in environmentally responsible practices, including participating in underwater clean-up events where they may collect trash to help maintain marine ecosystems, the act of collecting trash is primarily oriented around removal rather than collection as a valued or collectible item.

On the other hand, artifacts, fossils, and fishing gear may be collected under specific guidelines and circumstances. Artifacts can hold historical or cultural significance, fossils can provide insight into past life forms, and discarded fishing gear may be retrieved to prevent entanglement or pollution in marine environments. These items often hold value either scientifically or historically, which is why they are more commonly sought after by divers compared to trash.