Final answer:
Sonar is most practical for measuring distances between objects in the ocean, utilizing ultrasonic sound waves to determine the position of underwater items by the time it takes for echoes to return.
Step-by-step explanation:
Sonar, which is an application of ultrasound, is most practical for measuring the distance between objects in the ocean. The technology utilizes ultrasonic frequencies to send out sound waves that reflect off objects, allowing measurement of distance based on the time it takes for the echoes to return. This method is highly effective for submarines, ships, and oceanographers to determine the position of objects underwater, including the seafloor, other vessels, and large marine life.