It had been a productive day in regards to fish-catching, luncheon-eating, pipe-smoking, and nap-taking; and now, as the sun lowered itself towards the distant trees, and the gnats rose from the cooling, gurgling, chuckling waters of the River, and the swifts dashed among them, the two friends were returning to the Water Rat's snug hole in the Bank.
-- Narration (New Arrivals)

Importance: This bit of narration, from the opening scenes of the novel, introduces us to the lifestyles of Water Rat and Mole by illustrating the idyllic nature of the world they live in. Sentences like this one help to establish early one of the novel's primary themes, which is the pursuit of a peaceful, relaxing life. Ironically, Toad's lack of interest in this sort of lifestyle, shared by his friends, will get him into significant trouble later on.

Dear ladies [...] you are indeed welcome! We were just chatting, my friends and I, about...
-- Toad (Tea at Toad Hall)