A waterfall is the subject here, and the speaker treats it as something close to sacred. The opening lines describe water tumbling down a channel, its sound pouring out easily, as if it has done so for thousands of years and people have only just begun to listen. The speaker then imagines how pleasant it must be to be the water itself, bubbling happily as it falls.
The middle stanza holds the poem's central idea: the fall is always changing, yet always the same. Each drop is new, but the shape and sound stay constant, so the waterfall feels timeless. The repeated "continuously" mimics that steady flow.
In the last lines the speaker invites us to "dip ourselves in that stream" and dream alongside its eternity. By doing so, we can gain "a little bit of Heaven." The mood is calm, admiring and gently uplifting, with a sense of peace and wonder rather than drama.