Final answer:
Deep-water eddies are monitored by using sonar technology, which involves sending out sound waves that bounce off the seabed to determine the depth of the ocean.
Step-by-step explanation:
Deep-water eddies are monitored by using instruments that utilize sonar technology. Ships on the ocean make use of the reflecting properties of sound waves to determine the depth of the ocean. Sonar, which stands for Sound Navigation And Ranging, involves sending out a sound wave that bounces off the seabed. By measuring the time it takes for the sound wave to return, the distance from the ship to the bottom of the ocean can be determined.