If this land would enter, sacrifice a Swamp instead. If you do, put this land onto the battlefield. If you don't, put it into its owner's graveyard.

: Add

.

, Sacrifice a Swamp: Add




.
You have to sacrifice a swamp before this card is put onto the battlefield. And you have to do this no matter how it is put onto the battlefield.
The tap and sacrifice counts as tapping the land for mana.