## 1 Introduction  
Underwater acoustic communication (UAC) is an interesting research area with many useful applications. At present, UAC channels in shallow water are characterized by band-limitation, extensive inter-symbol interference, and a large Doppler spread. Shallow water is defined as water with a depth between 10 and 200 m. For a water depth of 20 m, the transmission range of 50 km, source depth of 19 m, and a receiver depth of 17.2 m, the multipath spread is 5 ms when using binary phase-shift keying (BPSK) modulation with a 17 kHz carrier frequency, and a 4 kHz bandwidth [1]. For UAC, higher frequencies lead to shorter communication ranges. [PERSON] et al. [2] investigated UAC characteristics using quadrature phase-shift keying (QPSK) modulation with a data rate of 27.2 kb/s, the transmission range of 1500 m, the transmission bandwidth of 21.25 kHz, and a carrier frequency of 85 kHz in a shallow water region. Indeed, robust and reliable underwater wireless networks are rapidly expanding to explore the undersea world [3]. [PERSON] et al. [3] demonstrated the concept of cooperative orthogonal frequency-division multiplexing (OFDM) UAC, underwater acoustic channel modeling, and an adaptive system design, with optimal power allocation and distribution, for short-range UAC. OFDM has been applied in standards for the digital subscriber line (DSL), Institute of Electrical and Electronics Engineers (IEEE) 802.11n, IEEE 802.16, third-generation partnership project long-term evolution (3 GPP-LTE), and LTE advanced standards. Filter bank multicarrier (FBMC), generalized frequency division multiplexing (GFDM), and universal filtered multicarrier (UFMC) are derived from OFDM principles [4]. FBMC adopts a subcarrier-based filter operation to achieve lower out-of-band leakage, whereas GFDM uses one cyclic prefix (CP) for many OFDM symbols to improve the bandwidth efficiency of data transmission. [PERSON] et al. [5] investigated several orthogonal modulation approaches, such as FBMC, GFDM, UFMC, and filtered OFDM for fifth-generation (5G) networks. Compared with traditional OFDM, advanced modulation technologies have high spectral efficiency, loose synchronization requirements, and flexibility to support transceivers with various transmission data rates. However, FBMC and GFDM transceivers using subcarrier-based filtering are more complex. For the UFMC scenario, subband-based filtering was utilized. [PERSON] et al. [6] expounded on the waveform design principles of UFMC and FBMC, which they reported as suitable for user-centric transmission. The high spectral efficiency of UFMC, a new data transmission method, makes it ideal for use in future 5G mobile networks. [PERSON] et al. [7] designed a UFMC system characterized by 80 subbands with 12 subcarriers each, 16 quadrature amplitude modulation (QAM), an inverse discrete Fourier transform (IDFT) with a size of 1024, and a Dolph-Chebyshev filter; they also demonstrated bit error rate (BER) performance in an additive white Gaussian noise (AWGN) channel. UFMC adopts the approach of filtering a block of subcarriers (subband) to reduce the transmission requirement of additional training signals and synchronization of complex systems; it can be applied to the Internet of things (IoT)/machine-to-machine (M2M) device communication. [PERSON] et al. [8] found that the symbol error rate for UFMC with QPSK modulation is better than that of OFDM with QPSK modulation at the same frequency offset. To overcome multipath fading channel effects in UFMC technology, researchers have considered foregoing the CP for QPSK modulation, 16-QAM, and 64-QAM [9]. UFMC is a novel multicarrier technique that has the advantages of OFDM while also avoiding its drawbacks, such as strict time and frequency synchronization and high out-of-band emissions [10]. Compared with OFDM, UFMC has better performance in addressing weaknesses using sub-band filters. [PERSON] et al.