1. An expendable underwater vehicle for use in training naval forces in anti-submarine warfare in ocean water, comprising: a body having a length along a longitudinal axis of about three to five feet and a diameter of about five inches, the body comprising a shroud at a rear end of the body which includes a propeller, elevators, and rudders; actuators for controlling the elevators and the rudders; an internal motor for driving the propeller; an internal guidance and control subsystem for implementing a predetermined path for the vehicle in the ocean water by controlling the motor and the actuators to cause the vehicle to conform to the path; an internal signal processing subsystem for simulating a submarine by generating signals representative of the submarine, causing corresponding acoustic signals to be transmitted into the ocean water, and varying the amplitudes of the acoustic signals which comprise a first acoustic signal having a frequency of about 450 Hz and a variable amplitude having a range of about 40 dB, a second acoustic signal having a frequency of about 600 Hz and a variable amplitude having a range of about 40 dB, a third acoustic signal having a frequency of about 720 Hz and a variable amplitude having a range of about 40 dB, and a fourth acoustic signal having a frequency of about 900 Hz and a variable amplitude having a range of about 40 dB; and an internal power source for powering the signal processing subsystem, the guidance and control subsystem, the motor, and the actuators.