Aquamorph Entity is a common Creature — Shapeshifter card from Planar Chaos (PLC), collector number 33. Current market price: $0.17 (foil $0.25), TCGplayer market prices via Scryfall.
As this creature enters or is turned face up, it becomes your choice of 5/1 or 1/5. Morph {2}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)