Underwater vehicle technology has been gaining in importance in the last few years. Large sections of the earth's oceans remain unexplored. The quest for energy resources under the water has given an impetus to develop fast moving underwater vehicles capable of traveling along a complex 3D trajectory. This book describes the development of a small autonomous underwater vehicle or AUV known as the Hydrocopter that can mimic the motion of a helicopter. A model was constructed and tested in a deep water tank at Memorial University of Newfoundland, Canada. Normally the development of a new idea can be an expensive process with no guarantee of a successful outcome. However, by using available components a relatively inexpensive model can be developed to test a concept. The book describes how off the shelf components can be used to design and develop models which can be used to generate creative ideas and at the same be useful in teaching practical engineering concepts. The book also explains control strategies employed for the hydrocopter.