Visited two huge fish wet markets in Okinawa last week. The variety and quality reminiscent of a miniature Tsukiji.
Not as focused on LIVE as Chinese. The seafood was nevertheless absolutely fresh and pristine.
Saw a clam that I can only describe as a baby Giant Clam. Cannot remember seeing this anywhere before.
A dozen restaurants on the second floor of one of the markets will cook your catch for you for a fee.
For cooked fish, Hong Kong hands down. For sashimi, Okinawa gets the nod.