Here's why:

* Sponges (Porifera): These simple animals rely on a system of water channels to transport nutrients and oxygen throughout their bodies. They lack a circulatory system with blood.

* Jellyfish (Cnidaria): Jellyfish also lack a true circulatory system. They are mostly made of water and rely on diffusion to transport substances throughout their bodies.

* Flatworms (Platyhelminthes): Flatworms have a simple circulatory system called a "gastrovascular cavity". This system is responsible for both digestion and transport, but it doesn't involve blood as we know it.

Instead of blood, these creatures have other methods for transport:

* Sponges: Water flowing through their channels carries nutrients and oxygen.

* Jellyfish: Diffusion across their thin bodies moves essential substances.

* Flatworms: The gastrovascular cavity transports both digested food and waste.

So, while these creatures are definitely alive, they don't have the same complex circulatory systems with blood that we see in more advanced animals.