In a steady state, waves with exactly zero amplitude do not typically occur in the sea, ocean, or rivers. Waves are generally caused by disturbances or forces acting on the water surface, and in a steady state, the system has reached a balanced condition where the wave generation and dissipation processes are in equilibrium.
However, it's important to note that the concept of "zero amplitude" is theoretical and might not be practically achievable due to various factors such as wind, currents, and other environmental influences. In natural bodies of water, there will always be some degree of movement or disturbance, even in a steady state, which could result in small waves or ripples with very low amplitudes.
In some specific cases, like certain highly sheltered or enclosed areas, the water might appear calm enough that waves are not easily noticeable or seem to have very low amplitudes. Still, even in these cases, there will likely be some minimal level of wave activity or small fluctuations in water surface elevation. Additionally, tidal effects and other long-period wave phenomena might contribute to a small but observable wave motion.
In summary, while the term "zero amplitude" is an idealized concept, there will always be some minimal wave activity or fluctuations in a steady state in natural bodies of water due to external influences and environmental factors.