Answer
The angular separation when immersed in water is $~~0.23^{\circ}$
Work Step by Step
We can write an expression for the angular separation in radians:
$\Delta \theta = \frac{\lambda}{d}$
When the arrangement is immersed in water, the new wavelength is $\frac{\lambda}{1.33}$
We can see that $\Delta \theta \propto \frac{1}{n}$, where $n$ is the index of refraction
We can find the angular separation (in units of degrees) when immersed in water:
$\Delta \theta = \frac{0.30^{\circ}}{1.33} = 0.23^{\circ}$
The angular separation when immersed in water is $~~0.23^{\circ}$
