Drinking water before ultrasound

I have my anatomy scan next week and I'm wondering if I really need to drink all that water? My instructions say to finish 32oz of water an hour before the scan. I'll be 19 weeks exactly the day of my scan, and I'm a very small girl (aside from my lil bump😍) Will they still be able to see clearly if I don't drink it all? Or will it have an effect on the clarity of the images? I completely finished the water for my first scan and was absolutely miserable and that one only lasted a few minutes! I really want to be able to enjoy this scan and not be wishing it was over the whole 30+ minutes. What did you all do?