How does Mark Twain use imagery in The Adventures of Huckleberry Finn?

Example of imagery..... the allure of life on the raft.

"Then we set out the lines. Next we slid into the river and had a swim, so as to freshen up and cool off; then we set down on the sandy bottom where the water was about knee deep, and watched the daylight come. Not a sound anywheres - perfectly still - just like the whole world was asleep, only sometimes the bullfrogs a-cluttering..."