Can I gain muscle if I drink a lot of water after a heavy workout session instead of consuming protein?

Nutrition. You need to both supply fuel (protein, carbohydrates, fat) to your muscle tissue after exercise for them to grow. But you also need to hydrate to help take away the toxins you produced during exercise.
Yes, not optimal. There is nothing wrong with drinking water after working out of any kind, but water alone does not contribute directly to muscle mass. Eating some protein within 30 min of completion helps improve recovery and may contribute to muscle building. Most importantly, follow a balanced diet, and avoid supplements; having lean proteins as a dietary staple is good for health and for athletic performance.