## 1 Introduction
However, environment data was scenario-specific and hard to acquire. In [24], [PERSON] et al. designed a graphical user interface (GUI) with configurable parameters to model UWA channels and showed channel effect over an acoustic signal. The GUI brought much convenience to constructing environment files and visualizing simulation results. Nevertheless, the accuracy of modelling might be deteriorated as empirical data, including Munk SSP, was used in the GUI. In this paper, three contributions are presented:  
1. A comprehensive simulation platform is designed to model and estimate realistic UWA channels. To maintain the accuracy of UWA channels, measured data such as SSP, sea bottom boundary, and sea surface boundary are interfaced from open databases. Therefore, the realistic UWA channels in most areas of the ocean can be modelled through BELLHOP model. Furthermore, the simulation platform is realized through MATLAB GUI, making building BELLHOP files and processing the result of simulation with configurable inputs user-friendly. In addition, the simulation platform provides a method of fixing the defect of the BELLHOP model when dealing with stochastic parameters, to simulate stochastic channels. In conclusion, the simulation platform is a powerful and efficient tool to simulate and analyse the UWA channels. 2. The modelling of UWA channels is combined with OFDM channel estimation. To study the modelling of UWA channels, a great number of researchers focus on analysing the transmission loss, CIR, and ray tracing, which show the transmission characteristic of UWA channels. Furthermore, bit error rate (BER) and mean square error (MSE) are key parameters in judging the performance of channel estimation. Hence the normalized CIRs of channels are computed in UWA channel modelling part and the comparison of performance of BER and MSE is made in the OFDM channel estimation part. Based on this framework, users can analyse the estimation performance of different modelling channels, modulation schemes, and estimation algorithms to assess the implementation scheme of the UWA communication device. 3. Based on the simulation platform, three simulations are conducted. Realistic UWA channels in the East China Sea are modelled to analyse the factors that could influence the performance of channel estimation. On the one hand, deterministic channels are modelled with different receiving depth and types of sea bottom to compare the performance of channel estimation. The result shows that channels with 10 m receiving depth and flat sea bottom yield optimal performance of channel estimation. On the other hand, a batch of channels is modelled with stochastic sea surface in different significant wave heights (SWH) and the result of channel estimation performance is synthesized. Overall, the channels with high SWH have a good average performance. The rest of this article is structured as follows. In Section 2, the article provides a brief overview of channel estimation in OFDM communication system. The implementation of simulation platform is demonstrated in Section 3. In Section 4, the effects of receiving depth, sea bottom boundary, and sea surface boundary on UWA channel estimation are analysed by modelling and comparison. Finally, a concise conclusion is made in Section 5.