Landwalk is a family of evasion abilities that makes a creature unblockable if the defending player controls a land with the specified type. Islandwalk, swampwalk, forestwalk, mountainwalk, and plainswalk are the most familiar versions.
Lord of Atlantis gives other Merfolk islandwalk, while Filth can grant your creatures swampwalk from the graveyard. Pairing Urborg, Tomb of Yawgmoth with swampwalk is a classic way to ensure opponents possess the land type you need.
