In ancient Rome, today is the feast day of Neptulia, set aside to honor Neptune, God of the seas and fresh water. The mythology of Neptune is somewhat a mystery, much like most of the deep sea remains to us. His early association with the Greek God Poseidon muddies the waters, so to speak. One aspect that differs in some detail is the more romanticized mythology of Neptune's ardent pursuit of his undersea queen, Salacia, a beautiful sea nymph.
My fascination with mermaids has come and gone over the years. I never went through a unicorn phase as a little girl, but I definitely went through a mermaid phase. My interest in them faded, returned in my teens, faded again, then recently returned. Over the last year or so, I have been reading and writing and reading and writing some more about the aquatic ladies (and gentlemen).
Once I started looking, I was surprised at just how ubiquitous mermaids are -- they're everywhere! In literature, mermaids appear in every genre, aimed at every age group. There are picture books aplenty, but also mysteries, teen adventure tales, romance novels, collections of mythology and folklore, art books, you name it.