In the given image, a person at point $B$ is drowning in the sea and needs to be rescued. If a person at point $A$, sitting on the sand on the beach, wants to reach the person in the water by covering the shortest distance, what should be the value of $\theta$?

Look at the image below. When the value of $\theta$ increases compared to the previous image, the red path from point $A$ to the sea becomes longer. On the other hand, when the value of $\theta$ decreases too much, the blue path from point $A$ to the sea increases. This means that for some value of $\theta$ between the blue and red paths, point $A$ will cover the shortest distance to reach the sea.