## 1 Introduction  
In recent years, with the rapid development of technologies such as underwater sensor networks and underwater vehicles, the scientific significance, economic benefits, and strategic position of ocean surveys have attracted increasing attention. Therefore, a proper light transmission simulation method suitable for underwater detection technology is urgently needed. Laser technology has been widely used in the fields of underwater target detection [1], recognition [2] and seabed mapping [3]. The early applications of laser-based underwater target detection mainly focused on the detection of seabed depth and seabed topography by airborne light detection and ranging (Lidar). Since the development of the airborne underwater Lidar system and related technologies has matured, the detection performance of underwater targets has been gradually improved. In the field of underwater detection, researchers have carried out a series of work to improve the performance of detection such as multiple scanning methods [4], high laser repetition frequency [5], photon counting [6] and polarization detection [7], etc. For the purpose of meeting the visualization requirements in many scenarios [8], laser underwater detection technology has gradually been integrated with advanced imaging technologies such as range-gated imaging technology [9], hyperspectral imaging [10], and polarization imaging [11]. Compared with the above imaging technologies, the range-gated imaging is able to capture the target at a specific distance based on controlling the relative delay between the detector gate and the laser pulse, which can filter out the influence of scattered radiation during the propagation process [12]. In addition, range-gated imaging has the advantages of a high S/N ratio, strong anti-interference ability, fast imaging speed, a simple structure and being unaffected by ambient light. It has become the most widely used underwater imaging technology against the current technical background [13,14]. Although, due to the inherent optical properties of seawater, light will be absorbed and scattered when transmitted in seawater, and the width of the time-domain impulse response caused by the multipath effect increases [2], which makes the propagating procedure difficult to solve by conventional and deterministic mathematical methods. At present, the main analysis methods of light scattering in water are divided into three types: analytical method, experimental method and MC simulation method [15]. Among them, the analytical method needs to set strict initial conditions and boundary conditions to obtain the analytical results. Different results will lead to different calculation results. On this basis, scholars proposed the use of the phenotype radar equation for analysis and calculation. This method has a small amount of calculation and intuitive results, but it is not suitable for quantitative comparative analysis of real situations in practical applications [16]. In addition, the analytical scope of experimental methods is often limited. On the basis of adding the auxiliary verification of experimental analysis, the method of cooperating with MC has been proved to be effective [17]. The MC method, which is a category of computational method that involves the random sampling of a physical quantity, is widely used for its flexibility in many different fields. It does not need to introduce constraints, boundary conditions or artificial assumptions, and can qualitatively analyze the trend of the detection system parameters and the influence of environmental changes on the results [18]. The laws are consistent with the real situation and can predict the actual results to a certain extent [19]. Therefore, MC simulation has become the main method for analyzing and studying light scattering in various scattering media.