DESCRIZIONE
An underwater detection apparatus is provided. The underwater detection apparatus includes a transmitter (2), a receiver (2), a target detector (11), a density index value estimator (12, 15, 16) and a size index value calculator (13). The transmitter (2) transmits a transmission wave. The receiver (2) obtains a receive signal based on a reflection of the transmission wave. The target detector (11) detects an underwater target object based at least in part on the receive signal. The density index value estimator (12, 15, 16) estimates a density index value of objects within a given area in a vicinity of the underwater target object. The size index value calculator (13) calculates a size index value of the underwater target object based at least in part on the density index value and a target object signal intensity representing a maximum intensity of the receive signal corresponding to the underwater target object. [Image Omitted]