What is the ruling on going into the sea with my friends if one of them or another man uncovers a part of what is between the navel and the knee, knowing that I follow the opinion of the majority that this is part of the 'awrah, and apart from the issue of intermingling and women's nakedness? And what is the ruling on going to mixed beaches with family or friends?

The majority of scholars hold that a man's awrah (private parts) is what is between the navel and the knee. However, the Dhahiris, Ibn Abi Dhi'b, and one narration within the Maliki school of thought consider the awrah to be only the two private parts (front and back). This issue is not one of consensus, but the view of the majority is the most preponderant. There is no harm in going into the sea with friends. You are requested to advise anyone who exposes any part of their awrah to cover it.