Murloc Paladin as an archetype really got started with the Journey to Un’Goro expansion. Gentle Megasaur really made this deck possible, but it’s particularly good in Paladin because of the powerful class Murloc: Vilefin Inquisitor. This allows you to turn your hero power minions into Murlocs which synergizes with your other Murlocs and takes advantage of Murloc Warleader.
Kobolds and Catacombs was one of the first sets not to have any Murlocs in it! However, this deck was strong prior to the release and got aggressive tools like Call to Arms, Val'anyr, and Corridor Creeper.
Check out our Murloc Paladin Deck List Guide to learn how to play this popular archetype.