Nosy Tanikely Island, Nosy Be, Antsiranana Region, Madagascar Protected by a submerged barrier-reef, Madagascar's northwest coastline is preceded by numerous coral reefs filled with cays of the 'Australian' type. Despite the cushioning of the waves' strength between the barrier-reef and the coast, the landscape clearly opposes the windward coraline plate ribbed by furrows and embryonic spurs, to a sandy triangular needle downwind the reef which welcomes tourist boats.