J/30 is a special kind of boat that people use for sailing. It's called a "racing boat" because it's really fast and made for going on adventures in the water while competing against other boats.
The J/30 is about 30 feet long and is designed to be really light and small so it can move quickly through the water. It can fit around six people inside, including the person steering the boat (called the "skipper") and the people who control the sails (called "crew members").
The J/30 has special features that make it go fast. It has a tall pole called a "mast" that holds up the sails that catch the wind and propel the boat forward. It also has a fin-shaped object called a "keel" that keeps the boat from tipping over while it's sailing.
When people race J/30s, they have different challenges to complete. They have to steer the boat around buoys (which are like big floating balls in the water) and try to beat the other boats to the finish line.
People really love the J/30 because it's so fun and exciting to sail on. It's like a big adventure and race all rolled into one!