Pull Against the Tide
Pull Against the Tide is a story written and illustrated by staringatsuns. It ran in Issue 58 at http://s2b2.livejournal.com/325809.html, and is mirrored at http://www.shousetsubangbang.com/mirror/pull-against-the-tide/.
From fairyninjas.wordpress.com: "A merman on a mission changes his means and goals for a while, and then meets an old frienemy, and then changes his goals a bit more, until everything is different, and there’s a happy ending for everyone we care about."
From http://harmless-one.livejournal.com/42989.html: "It's a different sort of mermaid story with a bit of a twist. Our main merman is...not necessarily likable, but the story works well, even if he's a hard guy to read about."