I was on a rented bicycle when I spotted this one. I was told that this was a water crow. It was actually waiting to prey. On being provoked by fishes, these birds dive into water to pull their live food out. Their water proof feather jacket allows them to remain dry.
It was during summers (not good for bird watching though….) and we were a bunch of 5 guys cycling through the sanctuary. But even then if lucky, water bodies can be a good place to track birds and for that matter even animals.