Nixen translates to "mermaids" or "water sprites". It's a whimsical and somewhat mythical word that stands out from the more common party themes in the song.
In the context of "Heisser Sand", the mention of "Strand voller Nixen" (beach full of mermaids) adds a touch of fantasy and allure to the typical beach party scene. It paints a picture of an idyllic, almost magical vacation spot, making it an enticing and memorable word for learners.
This song takes a famous old German chorus and drops it onto a Mallorca beach. The refrain keeps repeating "heißer Sand und ein verlorenes Land" (hot sand and a lost land), "und ein Leben in Gefahr" (and a life in danger), and the memory "dass es einmal schöner war" (that it was nicer once). On its own that sounds heavy and sad.
Then the verse arrives and the mood flips completely. The sand is not a desert of exile, it is El Arenal, the party strip where German holidaymakers go. The singer sends "ganz liebe Grüße" (best regards), talks about the glowing sun and a bit of "Amore", and admits he is already sunburnt and swollen by midday, wider than Grandma Lore.
The jokes keep coming. "Spanisches Wasser" (Spanish water) is really Cerveza, and twelve of them left him feeling a bit sick. There is blue sky, a beach full of "Nixen" (mermaids), and a drink straight after breakfast. The "danger" in the chorus turns out to be nothing more than too much beer and too much sun.
That contrast is the whole point. A serious sounding refrain about loss gets reused as a holiday singalong, so the "lost land" becomes the hangover you earned yourself. It is party music that winks at the sentimental song it borrowed from.