Red tide is a marine event where certain tiny organisms in the water, like algae and dinoflagellates, grow really fast, creating what's called a bloom. This can make the water change color, leading to what we know as Red Tide. Sometimes, these organisms can produce toxins or use up oxygen, which can harm or even kill marine life. So, when there's a lot of these organisms growing quickly in the water, it can cause problems for the ocean animals living there.