Roger Goh
Google
If you happen to wake early on a Saturday, or you plan it and get there between 6.30am and 7am, you will have a wide selection of fresh seafood. The shrimp tends to sell out early and long lines start to form more than an hour before they start selling. Prices for the seafood are reasonable. They used to be "cheap" (yes, I have been coming for years). The public parking lots will only require payment after 8am every day, so if you are there early to buy seafood you don't have to worry about paying for parking.
If you have young children, it will be a good educational trip to let them experience the early morning bustle, and see fishermen at work getting and cutting up fish. The number and types of fish vary from week to week, and sometimes you can buy bluefin sashimi, yellowtail, etc. There is also usually a good lot of stone crabs you can get every week.
During lobster season you could also find Pacific lobsters for sale. Be careful handling them as they are very vigorous and can jump a few feet off the kitchen countertop. The sharp hooks underneath can be really painful and cause real injury.
I think they also open on Sunday mornings, but I have been going only on Saturdays.
It is a cash only place, but there is an ATM conveniently located at the entrance in case you forgot to bring cash.