## 1 Introduction  
Reliable wireless communication systems with high data rates are essential for exploring the unknown underwater world. Conventional underwater communication systems are mainly based on acoustics. While the acoustic communication reach can span tens of kilometers, it fails to meet the high data rate requirements and typically can achieve only between \(100\,\mathrm{b}\mathrm{p}\mathrm{s}\) and \(100\,\mathrm{k}\mathrm{b}\mathrm{p}\mathrm{s}\), with rates decreasing over longer distances. Consequently, the demand for higher data rates has shifted focus to optical communications, especially for short and medium ranges. Optical wireless communications offer higher bandwidths, much lower delays and feature lightweight equipment [1]. However, despite these advantages, optical wireless communications encounter significant challenges, particularly in maintaining stable links between mobile vehicles. Incontrast to acoustic and RF communication systems, underwater optical wireless communications (UOWCs) require a direct line of sight (LOS). In addition, the small aperture size of the optical transceiver requires a high-precision pointing and acquisition system. Even small alignment errors can severely impair communication performance or lead to a complete loss of the connection, especially when laser-based communication is targeted [2; 3]. Hence, a pointing, acquisition, and tracking (PAT) system is necessary for establishing OWC links. PAT systems can be categorized into three main types: mechanical, electro-mechanical, and electronic. Mechanical PAT systems rely on gimbal mechanisms driven by motors, resulting in a robust but bulkier system. Electro-mechanical PAT systems use fast steering mirrors, which are lighter compared to mechanical systems but still suffer from vibrations and have limited pointing resolution and angular movement. In addition, researchers have proposed antenna selection schemes to mitigate fading and misalignment in underwater optical wireless communication links [4; 5]. For instance, a generalized transmit laser selection strategy is studied in [4] for vertical underwater links over Gamma-Gamma turbulence channels, where a multi-laser transmitter dynamically selects the most favorable laser branch. Similarly, the authors in [5] investigate cooperative non-orthogonal multiple-access techniques, highlighting how careful resource allocation can combat adverse underwater channel effects. Compared to advanced pointing, acquisition, and tracking (PAT) solutions, such selection-based approaches can reduce complexity under moderate misalignment conditions. However, they often require additional hardware or algorithmic overhead to choose between multiple lasers or antennas, which must be weighed against the performance gains. Electronic PAT systems, based on OPA antennas, offer low weight, high steering speed, and exceptional accuracy compared to other types, which makes them the optimal choice for our study. Additionally, the performance of OWC systems is strongly influenced by the properties of the medium through which the light propagates. In underwater environments, optical signals are subject to strong absorption, scattering, and turbulence, which further escalate the challenges [6]. A comprehensive channel model incorporating a wide range of underwater properties is essential for designing and evaluating the UOWC system. Our study aims to employ such a model by accounting for various environmental factors, including absorption and scattering in different Jerlov water types [7], as well as turbulence effects ranging from weak to strong. The used model considers the significant influence of temperature and salinity variations, kinetic energy dissipation rates, mean square temperature per unit mass of fluid, and viscosity on turbulence dynamics. By including these factors, we can achieve a more accurate and thorough understanding of UOWC channels. Building on this comprehensive channel model, we propose a system concept that is designed to overcome the aforementioned challenges.