Asterism

The Big Dipper, Summer Triangle, and Orion's Belt are asterisms.

Of the constellations, or asterisms. [...] It therefore became necessary to adopt a more general method of distinguishing them. This was accomplished by portioning out the heavens into imaginary figures, of men, birds, fishes, &c. called Constellations or Asterisms.

Like Pisces and Capricorn, Aquarius is located in that part of the sky known as "Astral Sea," a region inhabited by water asterisms such as Eridanus, Cetus (the Whale), and the Dolphin.