What is rafting seen by narrator in Three Men in a Boat?

I'm not sure I understand your question, but Jerome has the following to say about rafting;

After that, having acquired a taste for the water, I did a good deal of rafting in various suburban brickfields—an exercise providing more interest and excitement than might be imagined, especially when you are in the middle of the pond and the proprietor of the materials of which the raft is constructed suddenly appears on the bank, with a big stick in his hand.

Your first sensation on seeing this gentleman is that, somehow or other, you don’t feel equal to company and conversation, and that, if you could do so without appearing rude, you would rather avoid meeting him; and your object is, therefore, to get off on the opposite side of the pond to which he is, and to go home quietly and quickly, pretending not to see him. He, on the contrary is yearning to take you by the hand, and talk to you.

It appears that he knows your father, and is intimately acquainted with yourself, but this does not draw you towards him. He says he’ll teach you to take his boards and make a raft of them; but, seeing that you know how to do this pretty well already, the offer, though doubtless kindly meant, seems a superfluous one on his part, and you are reluctant to put him to any trouble by accepting it.