Sinaiya island is close to the town of Umm al-Qaiwain. It is 12 kilometres by 1 kilometres and comprises an admix of low sand dunes, intertidal flats and creeks, halophytic scrub and mature mangrove. Inland is the Khor al-Beidah, an expansive area of sand and mud-flats of international importance for its waterfowl.
Sinaiya is an inshore sand-bar, perhaps formerly a spit, and now severed at its northern end. The UAE's largest Socotra cormorant (Phalacrocorax nigrogularis) colony is found here, with over 15,000 pairs, probably the third largest colony in the world. There are less than 15 extant colonies known for the species, most in the UAE.
Arabian (mountain) gazelle (Gazella gazella)have been introduced to Sinaiya and appear to be prospering. Marine life, although thus far little studied, is remarkable for its abundance and diversity. Black-tipped reef sharks patrol the outer shoreline, while green turtles are ubiquitous in the inner leads in particular.
Although not formally protected, the island of Sinaiya, along with the adjoining Khor al-Beidah, is one of the largest areas of undisturbed and varied coastal environment remaining anywhere in the UAE.
Apart from evidence of occupation in the Late Islamic period, probably by fishermen, little archaeological evidence has been identified on the island, although coins from the early first millennium AD have been recovered.