To dream that you are drowning suggests that your feelings are pressing down too hard on you and that something you buried long ago is awakening. You could be moving too fast if you are attempting to dig into your subconscious. Slow down. If you drown and die, this represents a passionate rejuvenation. If you survive, then a relationship you are having trouble in will make it through.
To dream about someone else drowning indicates that you are investing too much in some situation that you cannot control. This dream may also indicate that you have lost your individuality. You can't tell the difference between the different personas you wear.
To dream about rescuing someone from drowning suggests that you have dealt with some feelings and attributes that are represented by the person drowning.