The do fly the fish in, flash frozen. The Oceanaire fish I had was definitely frozen. And fish that's been on a plane even cold for 8 hours isn't really fresh. Then you have another 2 hours from airport to restaurant, and then it sits there for however long.
And oddly enough, Hawaii doesn't have much fishing, the waters are too deep. When we visited, I thought I'd find good seafood there, but never have. It's the same as here pretty much. I found some ahi at a grocery they said was fresh and it may have been.
I was told that as soon as the catch comes on a boat, it gets frozen, immediately. The only exception, pretty much, is when a restaurant has its own fleet, they go out, collect seafood, and chill it, and return directly to the restaurant. (Aside from lobster etc.).