I had the same problem with a friend. Lets all not forget the most important factor here, how well can he swim without a board? I had a friend that I tried to teach and when I realized that he swam like crap, I refused to take him out anymore until he got swim lessons. Some people say they are "OK" swimmers, but that could be doggy-paddle or breast-stroke. Some people just don't get the freestyle stroke. If you see him freestyle just fine, then everyone else's advice sounds pretty good. Even if he knows how to swim, the ocean is a different beast and takes some time to learn and get used to. Good luck.