1. Description of random seas -- 2. Spectral analysis -- 3. Wave amplitude and height -- 4. Wave height and associated period -- 5. Sea severity -- 6. Estimation of extreme wave height and sea state -- 7. Directional characteristics of random seas -- 8. Special wave events -- 9. Non-Gaussian waves (waves in finite water depth) -- App. A. Fundamentals of probability theory -- App. B. Fundamentals of stochastic process theory -- App. C. Fourier transform and Hilbert transform.