PETG does not absorb water !
ALL filaments will absorb water to some level. Nylon is the most notorious one, but PETG also has its issues. As example, last Thursday I tried two PETG filament samples from Formfutura (received them in the post that same day). They came out totally messed up with steam bubbles when printed at 225 C. I have vacuum-dried them (70 C, 50-70 mbar for 8 hours) this weekend and will test them again coming Tuesday when I have time. I saved some of the extruded PETG with steam bubbles for taking pictures and comparison to give some feedback to Formfutura. I will post them here when I have them.