A racing shell is like a fancy boat that people use to go really fast in the water. It's long and skinny, with a shape that helps it move through the water quickly. Imagine a very long, narrow canoe that is much longer than a regular canoe.
Racing shells can be made of different materials, but they're usually very light because the lighter it is, the easier it is to go fast. The shell can be made of wood, fiberglass, carbon fiber or a composite material. These are all different types of stuff that people make things out of, like the materials that a toy is made of or the clothes that you wear.
A racing shell has a seat for each rower, and it can hold anywhere from two to eight people who row the boat. Some racing shells can even have a coxswain, which is a person who sits in the boat to steer and help the rowers with their technique.
When people race in a racing shell, they use special oars to row the boat. Oars are like big paddles that are attached to the boat. They have a long handle and a flat paddle on the end. The rowers sit facing the back of the boat and use the oars to move the boat forward through the water.
Racing shells are used in competition, with one shell racing against another. The winner is the one that crosses the finish line first. Racing shells are also used for fun or exercise, as it requires a lot of effort to row them fast.