Streambed Aquitects is a common Creature — Merfolk Scout card from Duel Decks: Merfolk vs. Goblins (DDT), collector number 18. Current market price: $0.21, TCGplayer market prices via Scryfall.
{T}: Target Merfolk creature gets +1/+1 and gains islandwalk until end of turn. (It can't be blocked as long as defending player controls an Island.) {T}: Target land becomes an Island until end of turn.