You may know them as traditional swim trunks. They usually have a lightweight elastic and drawstring waist and include a mesh or other quick-dry lining for extra support. Boxers hit around mid-thigh or slightly longer and come in a wide range of colors and patterns (often more subdued than you'll find in board shorts). They're classic, and like any classic piece, they bypass a trendy look in favor of other attributes, like a style that compliments most body types and a comfortable fit and feel. If you actually plan on swimming in your swim trunks, boxers manage to perform well in the water without looking too snug out of the water.