Communication with submarines is difficult because radio waves do not travel well through thick electrical conductors like salt water.
The obvious solution is to surface and raise an antenna above the water, then use ordinary radio transmissions. Early submarines had to surface frequently for oxygen needed by their diesel engines to charge their batteries. During the Cold War, however, nuclear-powered submarines were developed that could stay submerged for months. To communicate with submerged submarines several techniques are used.
Read more about Communication With Submarines: Acoustic Transmission, Very Low Frequency, Extremely Low Frequency, Standard Radio Technology
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“Our manners have been corrupted by communication with the saints. Our hymn-books resound with a melodious cursing of God and enduring Him forever. One would say that even the prophets and redeemers had rather consoled the fears than confirmed the hopes of man. There is nowhere recorded a simple and irrepressible satisfaction with the gift of life, any memorable praise of God.”
—Henry David Thoreau (1817–1862)