An inexpensive, do-it-yourself hydrophone for tracking aquatic animals is described. It can be used with or without a preamplifier, on small or large boats. A new mounting arrangement used on the bow of a 25-m tracking vessel is discussed. It was used successfully in coastal waters at cruising speeds up to 9 knots (5 m/sec) and at slow speeds during rough weather in 30-knot (15.3 m/sec) winds.