Answer
In water, the angular separation is $~~0.15^{\circ}$
Work Step by Step
We can find the new wavelength $\lambda'$:
$\lambda' = \frac{\lambda}{n} = \frac{589~nm}{1.33} = 443~nm$
We can write an expression for the angular separation:
$\Delta \theta = \frac{\lambda}{d}$
In water, the wavelength is decreased from $589~nm$ to $443~nm$
We can find the new value for the angular separation:
$(\frac{443}{589})(0.20^{\circ}) = 0.15^{\circ}$
In water, the angular separation is $~~0.15^{\circ}$.
