Legend of Manfin, The Journey, Book 1 - Legend of Manfin, #1

Almost every human knows manfin are a myth, fanciful tales created by drunken sailors. But for one human named Ashaw, a childhood encounter with the fairytale creature feeds a lifelong quest to locate the elusive being. After his grandfather's passing, he has the means to hire a crew and set off on his journey. Along the way, they meet up with a man named Ferrell, who has his own mysterious history with manfin.
Together, they search the sea, unknowingly followed by a ruthless crew. Hidden away in fear of discovery and on the brink of extinction, the manfin struggle to adapt, rewriting their oldest laws. In the midst of argument and uprising, a long-ago human encounter spurs a discovery. If the manfin can overcome their negative perceptions of humankind, they may have the key to repopulating their breed. But will the key be a new beginning or the ending of who they are?