The Crab Pot bundle consists of the following, and is located in the Fish Tank certificate in the Community Center.
You only need to collect 5 of the 10 items mentioned above to complete this bundle. The reward for completing it is three crab pots, which can be placed in bodies of water around the farm and Pelican Town. Placing them at the beach can be the most profitable option.
Tip: Keep a sharp eye out at the beach, especially after you fix the bridge at the east end for 300 wood. You can sometimes find oysters, clams, and mussels on the beach. And crabs are sometimes dropped as loot from chests in the mines, so you can get most of what you need for this bundle pretty early in the game without using any crab pots at all!