What does "wade through its lunar landscape" mean in this context?

Question

I would like to know what "wade through its lunar landscape" means in the following sentences:

In the afternoons we were free. Beniek and I and some other boys would go to the beach and swim in the cold and turbulent Baltic. Afterwards, he and I would dry off and leave the others. We’d climb the dunes of the beach and wade through its lunar landscape until we found a perfect crest: high and hidden like the crater of a dormant volcano. There we’d curl up like tired storks after a sea crossing and fall asleep with the kind summer wind on our backs.

• Tomasz Jedrowski, Swimming in the Dark, Chapter 1

In this novel which is set in the 1980's in Poland under the socialist regime, where homosexuality was socially unacceptable, the protagonist Ludwik (a university graduate) left Poland in 1981 to live in the United States of America. And he remembers what it was like back then in Poland, where he used to hang out with his friends including his first love Beniek in his hometown of Wrocław when he was nine years old. He also went to a trip for his First Communion, where he used to swim and "wade through" the "lunar landscape" on the beach with Beniek.

In this part, I wonder whether "its lunar landscape" means the the crescent form of sand dunes on the beach, or the beach's landscape on which moonlight shone. But, it was only afternoon when children swam in the ocean, so I believe it was not dark enough for the moon to shine, though it says "lunar"... so I am confused and wanted to ask you.

I am an English learner from South Korea. I would very much appreciate your help. :)

Answer 1

If the sentence was about crescent shapes like the moon, it would have said something like "moon-shaped" instead. If it was about a place on which moonlight shone, it would have said "moonlit" instead. In this context, "lunar" doesn't mean anything about the moon as we see it from earth - it describes something similar to the landscape of the moon itself.

Of, determined by, or resembling the moon.

_{-- "Lunar", Lexico (emphasis mine)}

One of the example sentences in the above dictionary source is "Mountains of rubbish are piled up to form a landscape that is almost lunar in its desolation." This shows the use of the word "lunar" in a similar context to the one you found. Some dictionaries also have a special entry for "lunar landscape".

Answer 2

I reckon this is a clever reference to a lunar crater that usually rises a dune high up until it is met with a hollow that looks "high and hidden like the crater of a dormant volcano". I find contrast used in this context as in "climb" and "wade" and the very mention of "dune" and "crest". After all it is how I would see it and I take it to the appearance of the moon(the moon's dark, cool, calm nature is used here with the afternoon that is a dormant volcano).