Watery Grave is a rare Land — Island Swamp card from Edge of Eternities Promos (PEOE), collector number 261p. Current market price: $10.01 (foil $11.89), TCGplayer market prices via Scryfall.
({T}: Add {U} or {B}.) As this land enters, you may pay 2 life. If you don't, it enters tapped.