The one that does not look like seaweed has fronds that are soft, inflated, branching tubes, hollow and gelatinous, like small red sausages or fingers of sponge. They are bright red to pinkish-red, sometimes with a translucent quality. They look like they belong in the animal kingdom, not the plant kingdom. They look like sponge or coral or something you would find in a tide pool that you would not want to touch. It is the alga of the strange shape, the one that blurs the line between plant and animal. What makes it special is the texture. The red sponge algae is soft and gelatinous, filled with a jelly-like substance. It is not crunchy like the sea moss or leathery like the ribbon kelp. It is squishy. You can press it between your fingers and feel it give, then watch it slowly spring back. It is the jelly of the seaweed world, the one that is soft and yielding, the one that feels like it should be alive. The red sponge algae is a red alga, a member of the Champiaceae family. It is one of the few seaweeds that is truly hollow, its branches are tubes filled with a gelatinous fluid. This fluid helps the plant stay upright in the water, providing buoyancy without the need for air bladders. Under a hand lens, the tubes are beautiful, translucent and filled with a pinkish gel. Biologically, the red sponge algae reproduces by releasing spores from specialised structures on its fronds. The spores are produced in small bumps on the surface of the tubes. To find red sponge algae is to find a cluster of soft, red tubes in the shadows. They look like sponge, like coral, like something from a different world. You can touch them, feel their squishy texture, watch them spring back. It is the jelly one, the sponge-like one, the one that looks like it belongs in a different kingdom, the one that proves that the sea is full of things that defy easy categories.