###### Abstract  
Underwater optical wireless communication (UOWC) systems provide the potential to establish secure high-data-rate communication links in underwater environments. The uniqueness of oceanic impairments, such as absorption, scattering, oceanic turbulence, and air bubbles demands accurate statistical channel models based on empirical measurements for the development of UOWC systems adapted to different types of water and link conditions. Recently, generalized Gamma and a mixture of two generalized Gamma probability density functions (PDF) were proposed to describe the statistical behavior of small and large air bubbles, respectively, when considering several levels of particle-induced scattering. In this paper, we derive novel closed-form analytic expressions to compute the bit error rate (BER) and outage performance using both proposed PDFs for various scattering conditions. Furthermore, simple asymptotic expressions are obtained to determine the diversity order of each scenario. Monte Carlo simulation results verify the obtained theoretical expressions. Our results also reveal that UOWC systems present lower BER and outage performance under more turbid water cases with respect to the tap water case due to the higher diversity order and despite the significant increases in pathloss at short link distances. Particle-induced scattering provides an inherent mechanism of turbid waters to mitigate air bubble-induced fluctuations and light blockages. UOWC systems, 2024 24 2532 2024 24 2532 2024 24 2532 2024 24 2532 202  
However, the empirical approach provides a more accurate and realistic depiction of the underwater optical channel, integrating realistic environmental conditions rather than relying on simplified theoretical assumptions. Therefore, reliable UOWC system designs for specific oceanic environments require a performance analysis based on realistic and experimental underwater channel models. Given the difficulty of conducting experiments in the open ocean, underwater optical channel models are typically developed in laboratory water tanks under controlled conditions. In this respect, several studies have focused on the experimental modeling of UOWC channels under different phenomena, such as random temperature and salinity variations or air bubbles [5; 6; 7; 8; 9; 10; 11] (and references therein). Numerous works have demonstrated the importance of these models by obtaining new closed-form expressions for evaluating the UOWC system performance under these experimental channel models. The vast majority of these works have concentrated on analyzing UOWC systems under oceanic turbulence by means of probability density functions (PDF) such as the Weibull distribution [12; 13], the Exponential-Generalized Gamma distribution [14; 15], and the Gamma-Gamma distribution [16]. However, although these models comply with current data of irradiance fluctuations due to the joint effect of thermohaline gradient and air bubbles, neither of them have been evaluated for optical power fluctuations due exclusively to air bubbles. In this regard, the thermohaline gradient can mask the real impact of air bubbles on the perturbed wavefront at the receiver. Furthermore, oceanic turbulence due to the inhomogeneous thermohaline distribution represents a minor drawback compared with air bubbles or the absorption and scattering effect in deep waters, as the temperature and salinity of the underwater medium tend to stabilize at constant values [17]. However, the origin of air bubbles is highly heterogeneous (cavitation of vehicle propellers, phytoplankton photosynthesis, or zooplankton respiration [18; 19]), and their presence can significantly distort the received footprint. Indeed, a few investigations have demonstrated that the performance degradation in UOWC links is due solely to air bubbles [20; 21]. In [20], the dependence of the bit error rate (BER) of a UOWC link using different orders of pulse position modulation on bubble density and bubble size is experimentally analyzed in a water tank.