1. A method for ultrasonic acoustic imaging of objects within a body of water, the method comprising the steps of: collecting a plurality of echo soundings into a computer-readable medium using conversion circuitry, the soundings produced by an ultrasonic transmitter and detected by an ultrasonic receiver, wherein each echo sounding comprises a plurality of echo signals, the echo signals corresponding to an apparent vertical depth, thereby forming an unfocused image; collecting into a computer-readable medium spatial location information of the transmitter and receiver using a location device and control circuitry, wherein said collected spatial location information is associated with each collected echo sounding; and forming a focused image by executing programming code on a programmable computing device, further comprising the steps of: selecting a focused signal spatial location wherein the selected focused signal spatial location is defined relative to said collected spatial location information associated with the echo soundings; selecting one or more echo soundings from said plurality of echo soundings; selecting an echo signal from each selected echo sounding, whereby the echo signal selection is determined by a calculation of which echo signal from the selected echo sounding corresponds to a focused signal occurring at the selected focused signal spatial location, wherein said calculation is based on the selected focused signal spatial location and on the collected spatial information associated with the selected echo sounding; combining the selected echo signals, whereby a focused echo signal is formed; and graphing unto a computer display device the focused echo signal based on the selected focused signal spatial location, whereby a focused image is produced.