On the North Shore, they have shrimp and prawn farms. The owners have "food trucks" all along the road (there are about 6 or 7). They are worth the time to wait in line. The red one was my favorite.
In addition, there are some incredible restaurants in Chinatown (I'm not sure if that's what it is called, but there are Korean, Chinese, Thai, Japanese, and others that are to die for.) They aren't too far from Waikiki (easily within cab distance). While there, be sure to check out the asian markets.
Speaking of markets, you probably should check out the International Marketplace.