I was reading this over and saw Then visualise how you wake up, drink the rest of the water, and remember your dream. Does that mean think about drinking the rest of the water or actually drink it?
Also for the levels of sleep, if you dont always fall into the deepest level due to like a bad cold or horrible allergies will that affect anything? I have allergies year round so I dont exactly sleep well heh would that affect anything?
It means, you visualise how you drink the rest of the water 
you drink the rest when you wake up
about the sleep levels, that I can’t answer.
Then let me try . I think that you do get to the deepest levels of sleep (but perhaps less) since this is the most needed part of sleep. I dont think anyone normal would survive long without any deep sleep. But perhaps your level of sleep is often light, and this is actually not a bad thing because becomming lucid here seems to be less hard then in deeper stages of sleep.