Drowning is a very traumatic incident.
Even drunk, your body will most likely wake you up as it desperately tries to stay alive by expelling water & trying to inhale oxygen & filling your lungs with water.
I was a nurse at a state hospital & had patients who had failed at drowning. Most were totally disabled & in a chronic vegetative state, unable to speak, take care of their physical needs including using the toilet & depended on nursing staff for everything including eating. That's a road that shouldn't be traveled.
You would be wise to look through the megathreads to find other accessible methods of less "risk" of waking up in a body that won't function as it should & being stuck in that body for what will seem an eternity!!
I do hope you're able to find your peace & am sorry that your life has brought you to this point of making such difficult decisions