Hypocotyls developing from the fruits. The hypocotyls are unridged unlike C. tagal.
Ceriops australis is a common mangrove, more typically at the rear side of the mangrove where the strength of the tide has been much reduced by other mangrove trees at the frontline! Like the other two species of Ceriops in FNQ, this genus is easily recognized by the knife-like stipules covering the developing leaf bud. Trees possess characteristic fluted roots and whitish bark. Telling the species apart however, particularly between this species and C. tagal requires looking at the flower petals. More on this when I get some closeups.
Was previously called Ceriops tagal var. australis.
Flower closeup
Leaf Whispering in the Tropics 