If you want to experience the high drama of fish buying, head to this auction at the United Fishing Agency. The fishermen bring their fresh catch in at 5:30am (sharp) Monday through Saturday, and buyers bid on a variety of fish, from massive tunas to weird-looking hapupu. Don't be surprised if you don't recognize much of the language the bidders are using; it is an internal dialect developed over decades, which only the buyers and the auctioneer understand. You'll be happy you woke up so early!
Note: The Auction is now open to the public only by tour. That tour takes places on Saturdays only throughout the year (with the exceptions of the month of December and early January). The cost is $25 per person, and includes visits to the docks to see the fishing boats unloading, with a discussion of sustainable fishing practices. For full information, click on the link above.