One of the day trips I took while I was in Cairns was out to Green Island. Green Island is a coral cay, which means that, unlike the islands I visited farther south in Queensland, this island is not a mountain rising up out of the reef; it is actually part of the reef. As a result, it’s lower and flatter than the Whitsunday Islands. It is also spectacularly beautiful and a great spot for reef walking.
The photo below is from the beach on Green Island, looking back toward the mainland.