Mermen's OilMermen's Oil is a special oil available from Merpolis and made from a certain substance found only in the deepest waters where only specially trained merboys can reach. This oil is the source of Mermen's fluidity and grace, it allows the body to curve and flex in ways a person normally can't, and even gives their bodies the gleam of a merman's skin.
That's why it's so expensive but also very much admired in the world by everyone, much like other beautiful rare things like gold, gems and so on. Mermen's Oil is one of these precious and rare things and so only very special dancers sometimes perform with their bodies oiled and it is considered a special event that is always announced beforehands so that many people could come to watch.
Aril was given a pot of Mermen's Oil for his birthday by his village's elder and it was the most precious and beautiful gift that Aril had received so far in his life. His eyes were shiny with happiness all day and he outdid himself dancing in front of the whole village's eyes.
Thanks so much to Jungle-Perils for suggesting the very nice idea about the additional effects of this oil!! :>