ASDIC
A device for detecting underwater objects is typically called a sonar device. Sonar uses sound waves to detect and locate objects underwater by measuring the time it takes for the sound waves to bounce off the object and return to the device.
Self Containing Underwater Breathing Apparatus
Underwater sound detecting systems are called hydrophones. These devices are used to listen to and record sounds underwater, such as those produced by marine animals or underwater activities.
Aqualung
Not without breathing apparatus.
self-contained underwater breathing apparatus
A SCUBA (self-contained underwater breathing apparatus) tank
Self Contained Breathing Apparatus Whereas SCUBA = Self Contained Underwater Breathing Apparatus
SCUBA stands for Self Contained Underwater Breathing Apparatus. The B stands for breathing.
Self Contained Underwater Breathing Apparatus
Aqualung
It stands for Self Contained Underwater Breathing Apparatus.