"Officials from BAE Systems and Qinetiq (the former UK Defence Evaluation and Research Agency) DERA have revealed details of collaborative research into torpedo sonar and signal processing techniques that form the basis for a littoral upgrade to the Royal Navy's (RN's) Spearfish heavyweight torpedo. Torpedo homing performance in the littoral has traditionally suffered as a result of poor acoustics found in the shallow water environment. For example, shallow water has more pronounced temperature gradients (particularly in equatorial regions), which distort the sound-ray path and can result in non-detection zones. Also, active sonar performance is degraded by the proximity of the surface and the bottom reflecting boundaries, while passive sonar suffers as a result of wave noise and marine life."