The nice thing about Honolulu is the option of walking, taxis or bus. Don't forget Uber too.
You can use TripAdvisor filters to locate seafood restaurants in Waikiki.
I just did a filter for
Restaurants, Seafood, Cheap Eats & Mid-Range. Next I chose Ranking from the tabs at the top. I would look at the menus and decide which fits your party.
Here's the top five Seafood rankings for Waikiki
(1) Hula Grill Waikiki $$ - $$$
(2) Doraku Sushi Waikiki $$ - $$$
(3) Sansei Seafood Restaurant $$ - $$$
(4) Tiki's Grill & Bar $$ - $$$
(5) Chart House $$ - $$$
Here's the top ranked five Seafood rankings when I include all of Honolulu (you can use TripAdvisor's map view to see how far).
(1) Ono Seafood $
(2) Uncle Bo's Pupu Bar and Grill $$ - $$$
(3) Hula Grill Waikiki $$ - $$$
(4) Duke's Waikiki $$ - $$$
(5) Nico's Pier 38 $$ - $$$
Nico's Pier has been mentioned on TUG but it's not within walking distance.
I always visit Sansei Seafood Restaurant when we're in town. It's located in the Marriott on the main shopping strip in Waikiki. It's Asian Pacific Rim cuisine. We always get the Miso Butterfish and Shrimp Dynamite appetizers. Their fried calamari and ahi poke appetizers are good too. They also have an early bird special on Sunday and Monday 5:30pm – 6:00pm (50% OFF FOOD AND SUSHI)
http://www.waikikimenus.com/happy-hours
http://sanseihawaii.com/waikiki/