  Underwater wireless optical communication is one of the critical technologies
for buoy-based high-speed cross-sea surface communication, where the
communication nodes are vertically deployed. Due to the vertically
inhomogeneous nature of the underwater environment, seawater is usually
vertically divided into multiple layers with different parameters that reflect
the real environment. In this work, we consider a generalized UWOC channel
model that contains$N$ layers. To capture the effects of air bubbles and
temperature gradients on channel statistics, we model each layer by a mixture
Exponential-Generalized Gamma(EGG) distribution. We derive the PDF and CDF of
the end-to-end SNR in exact closed-form. Then, unified BER and outage
expressions using OOK and BPSK are also derived. The performance and behavior
of common vertical underwater optical communication scenarios are thoroughly
analyzed through the appropriate selection of parameters. All the derived
expressions are verified via Monte Carlo simulations.
