In Underwater Sensor Networks (UWSNs) based on clustered architecture

cluster heads forward large number of data packets when they send data to the Sink using a single-hop or multi-hop mechanism.This mechanism can overload cluster heads

which soon become depleted of energy

causing coverage holes quickly.The LEACH-Coverage-U algorithm attempts to solve this problem

but because the cluster heads are randomly elected

this algorithm cannot solve this problem very well.In this paper

we propose a single-hop coverage-preserving routing algorithm (SCPR) for UWSNs.This algorithm first defines a metric of coverage redundancy (CR)

and elects the cluster heads according to this metric.A cluster head sends the aggregated data directly to the Sink.To reduce energy consumption and achieve higher network coverage ratio

we also propose a multi-hop coverage-preserving routing algorithm (MCPR)

where each cluster head prefers to select the node that has higher CR in the parent nodes as its next hop node.Finally

the aggregated data are sent to the Sink using multi-hop routing.Simulation results show that

compared to the LEACH-Coverage-U algorithm

both the SCPR and MCPR algorithms solve the problem that the cluster heads are randomly elected

improve the network coverage ratio

reduce network energy consumption and extend network lifetime.