Underwater sound propagation is governed by geometric wave spreading and seawater medium absorption. In an unconstrained deep ocean water column, sound radiates as spherical wavefronts where acoustic intensity decays inversely with the square of range (20 log r transmission loss). In shallow water or within the ocean sound channel (SOFAR axis), acoustic reflections from the sea surface and seafloor constrain the energy to cylindrical geometric spreading (10 log r loss).