The phrase “a primitive aquatic invertebrate that draws in water” is describing a sponge , specifically a simple aquatic animal that filters water through its body.

What the clue is pointing to

  • Sponges are among the most primitive animals, lacking true tissues and organs but still being multicellular.
  • They are aquatic invertebrates , meaning they live in water and do not have a backbone.
  • Sponges feed and breathe by drawing water in through tiny pores, filtering out food particles, and then pushing the water back out through a larger opening. This “drawing in water” is exactly how they are commonly described in basic invertebrate lessons.

Why it is not other invertebrates

  • Tunicates and other filter feeders also draw in and expel water, but they are usually described as “sac-like animals with siphons,” not as “primitive” in a simple school-level clue.
  • School quizzes and introductory resources nearly always use this exact kind of wording for sponges when teaching early animal evolution and simple body plans.

So if this is for a quiz, crossword, or classroom question, the intended answer is almost certainly: sponge.