how did george and harris mistake a young man in punt for jim ? How did they treat him ?

The young punter looked like Jerome. He was doing a comic job of navigating his boat. People laughed at him from both sides of the bank. Jerome thought this was rude.

I had not been sitting there long before my attention became attracted to a man in a punt who, I noticed with some surprise, wore a jacket and cap exactly like mine. He was evidently a novice at punting, and his performance was most interesting. You never knew what was going to happen when he put the pole in; he evidently did not know himself. Sometimes he shot up stream and sometimes he shot down stream, and at other times he simply spun round and came up the other side of the pole. And with every result he seemed equally surprised and annoyed.