The propagules and seedlings float. When they fall from the mangrove they might start growing below the tree they came from. Many will float away with the tide. Once they have rested in one place for a short while they will establish their roots and grow their first leaves. If they are lucky enough to have settled in a suitable place they might be able to grow into a new tree.
Some species of propagules or seedlings can survive for four weeks while others can still establish after four months.