Which Instrument is used to measure depth of ocean?

Fathometer is an echo sounder. An echo sounder is a device for determining the depth of the seabed or detecting objects in water by measuring the time taken for sound echoes to return to the listener. Endoscope – An endoscope is an illuminated optical, typically slender and tubular instrument used to look deep into the body and used in procedures called an endoscopy. Ammeter – An ammeter (from Ampere Meter) is a measuring instrument used to measure the current in a circuit. Anemometer - A n instrument for measuring the speed of the wind, or of any current of gas.