How do waves behave after reaching a velocity equal to the wind speed?

When waves reach a velocity equal to the wind speed, they experience a condition known as "wave-coupling," where the energy transfer from the wind to the waves tends to stabilize. At this point, waves do not grow indefinitely because they are no longer receiving additional energy from the wind at a rate that would promote continued growth.

Instead, they can still grow but at a decreasing rate due to the balance between energy input from the wind and energy loss due to dissipation and other factors like wave breaking. As waves approach the limit determined by the wind speed, the energy input becomes less effective in causing additional height increases, leading to an asymptotic behavior where growth gradually slows down.

Waves that are exactly at the same speed as the wind may reach their maximum height but will not continue to grow as before. This understanding is crucial in coastal engineering and marine studies where wave dynamics play a significant role in design and forecasting.

The other options suggest either stopping or starting to dissipate immediately, which would not accurately describe the transitional state occurring at this velocity match.