It can absorb sound waves, deceiving the sonar.
Scientists from the University of Pennsylvania presented a masking device designed to work underwater. It is a metamaterial that either absorbs sound waves, or forces them to circle the object, so on the sonar it will be invisible.
The technology is still in its early stages, but it has already been tested in the laboratory. For the tests, a steel meter pyramid was made, which was dipped into water and sent to it sound waves with a frequency between 7 and 12 thousand hertz. Usually sonar sends vibrations that are reflected from underwater objects and return to the detector, but the pyramid on it was not visible: the vibrations from it did not return.