I went with with the optical version of the theme, but used planar refractive aberration instead of chromatic aberration. My game is a rail shooter with underwater targets, and thanks to refraction, objects in water are deeper than they appear, and you must adjust your aim to where the targets actually are.
This is possibly the first game to feature physically-accurate planar refraction (using a new rendering method), so as well as being a realistic simulation of optical aberration, it is also a divergence from the usual mechanic of game water being a transparent sheet that can be aimed through like it wasn’t there.