Well... I'd say that Okinawa definitely has some special dishes. You can see a bunch of stuff
here.
They eat goya in Okinawa. It's called bitter melon in English. It looks like a bumpy cucumber, but it's really bitter. I can't say I enjoy eating it.


In my opinion the best Okinawan food is probably
champuru which is a mix of many different ingredients.
To quote from
Wikipedia:
Chanpurū (Japanese: チャンプルー) is a form of popular Okinawan stir fry dish, generally containing vegetables, tōfu, and some kind of meat or fish. Luncheon meat (such as SPAM or Danish Tulip), egg, moyashi and gōyā are some other common ingredients.
"Chanpurū" is Okinawan for "something mixed" and the word is sometimes used to refer to the culture of Okinawa, as it can be seen as a mixture of traditional Ryūkyū, Chinese, Japanese, Korean and North-American culture. It is thought to come from the Indonesian word "campur" meaning mixture.
Long a local specialty only found on Okinawa, chanpuru has in recent years through television shows and increased interest in Okinawan culture, spread to many restaurants on mainland Japan.
Also, there seem to be more pork based dishes in Okinawa than in mainland Japan.
I guess my favorite Okinawan food is fu champuru. I'm not exactly sure what fu is, it's shaped like a washer or bolt before you cook it, but it's good.
There's also Okinawan soba, but I'm not too fond of it actually.
Overall the local food is very good, and I actually prefer it to Japanese food most of the time.
John