In atolls, sandbanks particularly accumulate on the edges of passes, these openings of the barrier reef which allow the water circulation between ocean and lagoon and are traversed by currents. They go so far as to form islets of emerged sand providing support for a herbaceous sandy shores vegetation of Lepturus repens and Stenotaphrum dimidiatum dotted with shrubs of Casuarina (iron tree), Acacia simplicifolia (acacia with a simple leaf) or bushy Scaevola taccada.