I’ve recently had my first experience rowing in a canoe and I noticed that when I finish rowing, there is always 1(sometimes more but usually 1) spinning moving hole in the water. it usually gets filled up with water nearby after a few seconds but they sometimes last around half a minute. this phenomena seems to happen when you put an object in a liquid, move it and then scoop it out of the water(tried with soup). is there a reason why that happens? maybe some well known physic stuff.