Yes, all you have to do is have two Marrill, give the female one a sea incense from Mt. Pyre. It actually doesn't matter which one is holding the sea incense as long as one of them has it. I gave the sea incense to my male Marill and I still got an Azurill. Of course you have to place them into the day care center or there is no point in any of this.
In the post story.
Pokémon that can be found in the Great Marsh Safari Zone are ones such as Bibarel, Wooper, Starly, Budew, Quagsire, Marill, Bidoof, Psyduck, Auzrill, Noctowl, Hoothoot, Marill, Skorupi, Croagunk, Carnivine, Golduck, Roselia and Staravia.