## 1 Introduction  
With the continuous growth of global economic and military needs, the development and utilization of marine resources has become one of the main driving forces of the new scientific and technological revolution. The demand for higher transmission rates and longer distances in underwater wireless communication technologies is increasing [1]. Compared with more mature underwater acoustic communication, underwater wireless optical communication (UWOC) has the advantages of high speed, small delays and low power consumption over short distances. However, the optimal transmission window for optical beams in seawater is limited to the blue-green spectrum. The optical properties of the each component in seawater are mainly determined through the absorption and scattering properties of light [2]. As the distance between the transmitter and receiver increases, light experiences greater absorption and scattering, which severely affects signal quality. The degree of attenuation affects the transmission rate and range of the communication system, making UWOC transmission more challenging. Therefore, a key challenge for the next generation of UWOC systems is optimizing the system to achieve maximum transmission capacity based on the transmission distance between the receiver and transmitter [3]. This paper studies an adaptive control technology that can adapt to changes in the underwater communication environment. In recent years, adaptive transmission technology has been widely used in UWOC systems, with the main focus on power, modulation mode, coding efficiency or a combination of these parameters. In [4], an algorithm was designed to adaptively adjust the beam width and transmitter power to achieve reliable real-time long-distance video transmission. Autonomous underwater vehicles (AUVs) are used to establish reliable communication, addressing the shortcomings of relay technology in emergency situations and enhancing the stability of optical links. However, increasing power and expanding the beam width may reduce communication efficiency. In order to reduce the transmission power required and solve the significant attenuation of light during underwater transmission, in [5], a photomultiplier tube (PMT) with a strong low-light detection capability was used to receive signals. Experiments in a 10 m indoor water tank verified the system's reliability; it is reasonably predicted that the PMT has the potential to achieve long-distance underwater communication. When the incident power is too high, the PMT may be saturated, leading to signal distortion. Neutral density filters can attenuate the incident optical power, but their operation accuracy is low. In [6], it is pointed out that the transmittance of a liquid crystal light valve (LCLV) can theoretically achieve continuous variation between 0% and 100%, allowing for more precise power control. By dynamically adjusting the LCLV and the PMT gain, the dynamic range of the received optical power is extended by 68 dB. The study employed on-off keying (OOK) modulation. However, considering the requirements for transmission efficiency and interference resistance, more complex modulation schemes are needed. In [7], an integrated binary phase shift keying (BPSK)/quadrature phase shift keying (QPSK) switchable transmission and reception method was proposed for free-space optical (FSO) communication. It adaptively switches between BPSK and QPSK based on different channel conditions. Stable communication is achieved and the channel's capacity is improved. The distance between the transmitter and receiver is one of the key factors affecting signal quality. In [8], for visible light communication (VLC), a system was designed to select pulse-position modulation (PPM) or pulse-amplitude modulation (PAM) based on the signal-to-noise ratio (SNR) to meet bit error rate (BER) requirements.