Pfiesteria is a type of tiny creature that lives in water. It can be very dangerous because it produces toxins that can make other creatures, including fish and humans, very sick. When they are in the water, Pfiesteria grow into different shapes, and some people say they look like tiny jellyfish or even little flowers!
If people or animals come into contact with water that has Pfiesteria in it, they might experience problems like rashes, headaches, and even memory loss. In some rare cases, they might even die. Scientists are still trying to understand how to protect people and animals from this creature, but right now, the best thing to do is to avoid contact with any water that might be contaminated with Pfiesteria.