Mangroves live in areas with some protection from waves. Along the coast the species of mangroves facing the sea can cope with larger waves than the species growing behind them. Rivers don’t have the large waves along the coast. River mangroves are much more sensitive to waves.
When boats speed through water they set up large bow waves. These waves batter the mangroves and move around the floating mangrove seedlings. As the sea level rises these added waves will push the seawater even further inland.