What is often the first visual sign of an approaching hurricane?

A raging sea

Even before the wind's force is felt, the unusual agitation of the sea can signal the approach of a hurricane. This agitation is caused by the immense force of the hurricane, which moves large amounts of water well before its center reaches the coast. Sailors of old were well aware of this harbinger of violent weather, using the observation of waves as an essential navigational tool. In today's context, monitoring marine conditions provides scientists and authorities with a valuable way to warn coastal populations of an approaching hurricane, helping to reduce risks to life and property.