There's about 4.6*10^46 molecules in the ocean. There are about 8.5*10^47 cubic meters in a cubic light-year

Surprisingly close orders of magnitude

For reference, the closest next star system is 4.25 light years away. The diameter of our Galaxy is about 105 700 light years, with a thickness of about 1000 light years (much less than the diameter, since our Galaxy lies on a plane)