Near the end of a dive as I was heading to the exit point, I noticed the exposed mantle of a Pacific oyster (Crassostrea gigas). There were many oysters clustered together and I was surprised by the varying shell shapes between them. The Pacific oyster is from the Pacific coast of Asia and has been farmed in Japan for hundreds of years. Over time it has been introduced to other areas such as Australia, New Zealand, Europe and North America, and is now the most commercially harvested oyster in the world. The Pacific oyster was introduced to the Pacific coast of the United States in the 1920’s, and has a range that extends from central Alaska to central California. This oyster can reach an adult size of 15.7 inches (40 cm) in length.