It took me a long time to get half the way, and by that time my clothes were very heavy and I was very tired.

Moreover, my man was still invisible.
Of course I could not turn back.

Even if I did not succeed in fishing him out, it was a "gallant attempt," which would be almost as good.
Partly to see how the crowd was taking it, and partly to rest myself, I turned over on my back and floated.

This do doubt was a tactical error; for as a rule a hero does not float out to save any one's life.

In my case it did not much matter, for the first thing I perceived as I turned was my drowning man's head bobbing up merrily between me and the shore, having enjoyed his long dive and wholly unaware of the "gallant attempt" which was being made to rescue him from a watery grave.
As he caught sight of me, however, floundering on my back, and scarcely able to keep my head up for the weight of my clothes, his face became alarmed.