What is the narrator referring to when he says,"strange nature voices all around them. Truer meaning of life than this."

I believe that he means when you first go out on the boat, the river will seem so calm and silent. Later, when you've become used to eat the noises you never hear become apparent....... the voices of nature; the birds, the water, the animals, the rustle of the trees along the bank. Nature in its purest form is far more meaningful than than the hustle and bustle of the world we create.