The kind of sensors you can put on a plane or satellite simply can’t penetrate seawater effectively. It absorbs radar, dissipates heat and light. Sonar sound wa

The kind of sensors you can put on a plane or satellite simply can’t penetrate seawater effectively. It absorbs radar, dissipates heat and light. Sonar sound waves in air mostly just bounce off the ocean surface. This is why submarines are so stealthy and therefore militarily useful. As long as they stay quiet they’re almost impossible to detect without using relatively short range active sonar.