I thinking you're referencing Snyder here with rip-rap, and his "each rock a word / a creek-washed stone". So, we're on the lake, but it's not making poetry as it beats (laps) against the rip-rap, no matter how much the N tries to hear it. Which suggests a flat N, not engaging with the natural beauty around him, and maybe feeling over-taut like the spider's webs, an image that gives a sense tension to the day.
I like that there are two ways of reading 'beating' here. The first, as above, is that the water isn't making the sound of poetry as it laps against the loose stones. The other is that the water isn't surpassing poetry: the world's not living up to the poetry that's written about it.
'champagne' in the title does tends to make me imagine him lakeside -- on the rip-rap -- with a glass of champagne and a poetry book: a copy of "Rip-Rap and Cold Mountain Poems", say. Then the line suggest that his surroundings don't beat reading poetry on the rip-rap. That might suggest he's enjoying the book, and I prefer to imagine him tense and miserable -- I have a fondness for miserable N's, I guess -- so I see him without a book, not especially enjoying his champagne, and the comparison to poetry implying a let-down more than anything else.
I don't know that I have nits really. I enjoyed reading and thinking about it.