The Columba Coin is found in Gatama Atoll, at co-ordinates F-6. This coin's "Shine Spot" is located in a patch of twig-like coral on the ocean floor relatively close to the round island that's located at F-5. This Shine Spot also contains two Singular Bannerfish.
"Columba" is latin for "dove".
In real life, Columba is a small constellation located south of the constellations Lepus and Canis Major. It was formed by a Dutch astronomer named Petrus Plancius to differentiate the stars near Canis Major.