Deeproot Waters is a uncommon Enchantment card from The Lost Caverns of Ixalan Commander (LCC), collector number 152. Current market price: $0.26, TCGplayer market prices via Scryfall.
Whenever you cast a Merfolk spell, create a 1/1 blue Merfolk creature token with hexproof. (A creature with hexproof can't be the target of spells or abilities your opponents control.)