Internal waves propagating in electrically conductive seawater induce weak secondary magnetic fields in the presence of the earth's magnetic field. The two-dimensional (frequency and wave number) magnetic induction spectrum caused by ambient internal waves is estimated by using the Garrett and Munk model spectrum of ocean internal waves. Because it involves convolution integrals over depth, the magnetic induction model spectrum depends on good estimates of the vertical coherence of internal wave motion. It is demonstrated that the vertical coherence scaling predicted by the Garrett and Munk model shows adequate agreement with field measurments. The predicted power spectral levels of magnetic induction are sufficiently large that magnetometry is a potentially useful oceanographic tool.