Answer
The diver should look at an angle of $48.75^{\circ}$ to see the setting sun just along the horizon.
Work Step by Step
Using Snell's law,
$n_{w}sin\theta=n_{a}sin90^{\circ}$
or, $sin\theta=\frac{1\times1}{1.33}$
$\theta=48.75^{\circ}$
Hence the diver should look at an angle of $48.75^{\circ}$ to see the setting sun just along the horizon.
