It is a Ryukyuan language, part of the Japonic language family, but it is not mutually intelligible with Standard Japanese. It is considered a distinct language, with its own unique grammar, vocabulary, and pronunciation.
However, it is important to note that Standard Japanese is also widely spoken in Okinawa. This is due to the historical influence of the Japanese government and the prevalence of Japanese media.
So, while Okinawan is the native language, Okinawans also speak Japanese, and the level of fluency in each language varies among individuals.