He fell past it right into the water and that brought him to his senses, kind of.

So he sputtered and groped around till he happened to clutch the Indian dugout and it rolled over with him and the anchor that we had laid in it with a rope to hold it fast to the houseboat, the anchor rolled out, and the first thing he knew he was drifting up the river, hanging onto the dugout for dear life.
He was feeling so weak and sputtering so on account of his lungs being all filled with smoke, that he couldn't shout and after a while he drifted up on the bar near Second Bend.

Then he got the dugout set right side up on the mud while he bailed it out by splashing in it with his hands and afterwards making them into a cup.
After that it was easy drifting up stream and when he got to about a quarter of a mile below the boathouse, he managed to paddle over to the shore and then he pulled himself along by holding on to the weeds and things.
"You had a pretty narrow escape," Pee-wee said.
"It was a narrow boat, why shouldn't he have a narrow escape," I said; "I had a good wide escape, anyway." "Didn't you have your hat with you to bail with ?" somebody asked Artie.
"All I had was my copy of Initiation Drill," he said.
"Why didn't you drill a hole in the boat then," I said.
"What for ?", Pee-wee shouted.
"So the water could get out as fast as it came in".
"What are you talking about?
You're crazy!" he yelled.
"There should be two holes in every boat," Connie Bennet said, in that slow way he has; "one for the water to come in and the other so it can get out." Gee-williger! You should have seen Pee-wee.
Anyway, I suppose you think by this time that we're all crazy.

I should worry..