Portuguese Water Dogs are classified under the working Dog class meaning they are a highly energetic dog and intelligent. Hence, what this really means is they need plenty of exercise, and mental stimulation. Otherwise, left to their own devices could be destructive. No doubt you have done some research and already know this. On the other hand, their intelligence lends to learning quickly, but never underestimate they could outsmart their owner when one becomes lackadaisical. Therefore, obedience training is a must.
Subsequently, my experience has been they make great companions and guardians, learn very quickly (both good or bad behavior), very loving and extremely loyal. Furthermore, their inherent retrieving aptitude leads to a lot of mismatched socks and mittens, as well as, shoes and misplaced hats. However, on the more serious side they can get a bit nippy as they are learning what is acceptable. Learning this begins with mother and litter mates.