https://en.wikipedia.org/wiki/Optimist_(dinghy)

The Optimist is a small, single-handed sailing dinghy intended for use by young people up to the age of 15.

The Optimist is one of the two most popular sailing dinghies in the world, with over 150,000 boats officially registered with the class and many more built but never registered. It is sailed in over 120 countries[1] and it is one of only two sailboats as an International Class by World Sailing exclusively for sailors under 16.[2]