Reliable communication between aerial platform to underwater has become increasingly important for applications including ocean biological sensing, offshore oil and gas exploration, detection and removal of sea mines and subsea Internet and Things (IoT) [117]. In the particular case of deep-sea hydrocarbon exploration, the autonomous underwater vehicle (AUVs) needs to continuously dive into the deep-sea water to collect data from underwater sensors and resurface to transmit the collected data to the above water platforms. As the vast area of sea bed needs to be explored, this process becomes very time consuming and costly. Instead, the availability of a technology enabling the communication across the air-sea interface would ease the process in terms of time and cost. Similarly, the subsea IoT system, performing several tasks such as detecting early sign of tsunami, monitoring the health of underwater animals, surveying shipwrecks and crashes and ecological provinces, requires wireless communication across the air-sea interface and within the water column. Moreover, the cross medium communication finds crucial applications in defence and security. For example, the communication between airborne/ship-based drone and submerged submarine, without compromising the stealth capability of the submarine, requires the communication signal to be transmitted from underwater to above-surface and vice-versa.

The present study aims to model the channel characteristics of a downlink optical wireless communication system from above sea surface to underwater in presence of irregular surface waves, bubbles, absorption and scattering due to the particulates and medium inhomogeneity using Monte-Carlo numerical technique.