Modular distributed system for the acoustic detection of underwater threats in a sensitive zone

An acoustic detection system (100) for detecting targets that are at least partially submerged in a sensitive zone defined in relation to an infrastructure, characterised in that the system comprises at least one multistatic detection group, each multistatic detection group (3) defining a detection zone and having: a submerged transmitter (31) emitting at low frequencies; and a plurality of submerged receivers (32) comprising at least two receivers, wherein each receiver of a given group forms a bistatic pair with the transmitter of the group, each bistatic pair generating an elementary detection zone (320) surrounding a shadow zone (321), the detection zone of the group being formed by the entire set of elementary detection zones of the receivers in the group, and the shadow zone (321) of each receiver in a given detection group being at least partially covered by the elementary detection zones of the adjacent receivers of the detection system.