For underwater acoustic communication

the bandwidth is rigid restricted by transmission regions.In this paper

we research the relationship between the available bandwidth and the transmission distance

and propose a bandwidth balanced routing protocol

for underwater acoustic sensor networks (UASNs).When transmitting packets

it always selects the branch (from the next-hop node to the sink) whose available bandwidth is maximal

thus also reduce the congestion and keep balance of sensor nodes energy consumption in some degree.The simulation result shows that the proposed protocol could implement the bandwidth balance of all branches in whole network

and the energy consumption balance

then prolongs the lifetime.