Sandy Island is a tiny uninhabited islet near the airport of Carriacou Island, Grenada. A water taxi from Paradise Beach costs US$15 per person. This is expensive for a 5 minute ride, but it is worth it. There is no a living soul during the hurricane season (from June to October). But there are a lot of boats on the mooring in the high season. So the place becomes not so secluded. There is a great lobster bar, - unfortunately not cheap. The beach itself, as well as snorkeling are pretty nice, but far from the best compared to some other Caribbean destinations. Perfect for a half day visit. Shore and seabed: sand, stones. 
There are no hotels on the Sandy Island, while overnight camping is prohibited. However, on the nearby Carriacou Island, there is a good choice of hotels with rooms' rates starting from US$70 per night.