Final answer:
SONAR, which stands for Sound Navigation And Ranging, is the technique used to map the ocean floor's depth by measuring the time it takes for reflected sound waves to return to the ship.
Step-by-step explanation:
The technique that directs sound waves toward the ocean floor to map its depth is called SONAR, which stands for Sound Navigation And Ranging. Ships utilize this technology by sending out a sound wave from a transducer, which then reflects off the seabed and returns to the ship. The time it takes for this echo to return is measured, and since the speed of sound in water is known, the distance to the ocean floor can be calculated by multiplying the velocity of sound by half the time it took for the echo to return. This is essential for understanding oceanography, conducting seismic surveys, and for the use of submarines and exploration of marine habitats such as coral reefs without disturbing them.