An active sonar system consists of a source emitting a sound pulse (ping) and a receiver listening to the reflection of the wave on a target, known as the echo. Such a system is further divided into two distinct configurations. The first one, named monostatic, is made up of a collocated source and receiver, while the second one, referred to as bistatic, is based on a non-collocated source and receiver. To this extent, a Multistatic Sonar Network (MSN) is thus comprised of a set of sources and receivers deployed across a given Area of Interest (AoI), which, taken pairwise, form sonar systems in monostatic and/or bistatic configuration. In this paper, we therefore propose an efficient two-phase greedy heuristic to solve the Area Coverage (AC) problem in the scope of MSNs, a special case of Wireless Sensor Networks (WSNs), while taking into account existing coastlines. For this problem, the objective is to determine the optimal spatial layout of the MSN, i.e. the one that maximize the overall coverage of the AoI with regard to a limited number of sensors and a given probabilistic detection model. Furthermore, we use a Mixed Integer Linear Program (MILP) from the literature as a reference for the numerical experiments conducted on a dataset of diversified instances. The latter were specifically derived from Digital Elevation Models (DEMs) of AoIs selected throughout the globe and in such a way as to encompass a wide spectrum of peculiar geometric situations.