Complete 20 of the fishing world quests.
The quest "Mounted Shark Fishing" has been removed from this achievement as of patch 7.2 and no longer exists in the game.
As of today, this achievement is still not awarding any achievement points. Armory still lists it as zero points earned and in-game shows the Feat of Strength shield instead of a point total. Reported it as a bug as it appears this was overlooked when the achievement was fixed with 7.2. (The earliest report I could find shows that it had no point total in-game as far back as November 2016.)
Alrighty fishermen, the WQ Lively Runescale Koi is finally up on the NA servers!