Is a man's 'awrah (private parts) what is between the navel and the knee, or what is below the navel to above the knee, and is it permissible to go into a mixed-gender sea wearing swim shorts (a 'short') that show the navel and a part of the area above the knee?

A man's 'awrah (intimate parts that must be covered) is what is between the navel and the knee. The navel and the knee themselves are not part of the 'awrah. This is the view of Malik and Shafi'i. What is between the navel and the knee must be covered. It is not permissible to expose any part of the thigh or anything below the navel. If this occurs in a mixed-gender environment, then it is not permissible.