Related Clues:

• It's found on board ships on a recce
• Underwater navigation device
• Arson (anag.)
• System for the detection of objects under water
• Equipment carried by sailors on a raft
• Way of locating cycling crime?
• Ocean tracker
• It might pick up a big fish
• Means of detecting boy raised in crime
• Some bat's on a ride with its guidance system
• Bat's guidance system
• Bats navigate with it
• Device with blips
• Method of investigating something fishy?
• Echolocator