Acoustic signals have low absorption rate and face a high end-to-end delay because of low propagation speed in UWSNs. In addition, different noises, doppler effect and path losses introduces high EC and Bit Error Rate (BER). This BER decreases the reliability of data packets during transmission which results in high EC [2]. According to the authors in [3], acoustic signals are powerful near the signal's origin and get attenuated from noise. Additionally, noise intensity is minimum in deep water and maximum in shallow water. Therefore, minimum path distances eliminate the problem of packet redundancy and high energy dissipation which result in fewer collisions and packet retransmissions. Sensor node's battery life is an important factor for routing in UWSN. An energy-efficient routing protocol is required to minimize the EC, maximize the data collection, and enhance the reliability of data with affordable delay. The main objectives of protocol designing include:  
* Energy-efficient network
* Maximum data collection
* Reliable data delivery
* Affordable delay
* Required packet received ratio
* Efficient route selection with least number of active nodes  
Many researchers proposed different protocols to enhance the capabilities of UWSNs. For instance, efficient sink mobility is presented in [4], reliable data transmission is achieved in [5] and direct forwarding mechanism is proposed to reduce void holes and EC [6; 7]. Linear forwarding is adopted with single path and multiple paths to transmit data packets from source to destination for minimal EC [8; 9]. In the same way, geographical routing is globally accepted due to its scalability and simple implementation methodology. Somehow, if these packets survive from energy holes, different noises existing in their path make the packets erroneous. Therefore, data is sent through multiple paths using binary tree generation which decrease the chances of data corruption with possible energy overhead. In this work, two forwarded multi-path power control protocols are proposed: SPF-Three and BFS-SPF-Three. These protocols forward the data packets with the aim of eliminating retransmissions. It also minimizes the EC and RPER with an affordable delay to avoid the void holes. End-to-end delay is increased due to retransmissions. These retransmissions effect the performance of underwater network in terms of minimum Packet Received Ratio (PRR). To encapsulate the EC problem, network is divided into different layers by adopting the shortest path towards the destination. Data packets are uni-casted from relay nodes and multi-casted from cross nodes. This idea follows a greedy approach for transmitting the data towards the destination. Proposed protocols confirm 3-hop neighbors for data transmission and after confirmation, they choose the next hop neighbor as a current forwarder. This selection of next hop helps in avoiding the void hole regions to prolong the network lifetime with reliable data delivery. Abbreviations and acronyms with their notations are mentioned in Tables 1 and 2, respectively. The main contributions of proposed protocols are summarized below:  
* Two routing protocols are proposed: SPF-Three and BFS-SPF-Three
* Avoid void hole regions during the routing
* Opportunistic routing for minimum EC is performed
* Binary tree concept is implemented to avoid the packet collision
* Efficient route selection with least number of active nodes, minimum RPER and affordable delay The rest of the paper proceeds as follows: Section 2 covers the literature review of the state-of-the-art work and system model of proposed protocols is presented in Section 3. Simulation results, feasible regions and performance evaluation parameters of proposed protocols are explained in Section 4. Finally, Section 5 presents the conclusion and future work of the paper.