Spearfishing help?

This weekend some friends and i may go spearfishing. One of my friends is more llike a brother to me. We are fishing together alll the time and i would like to teach him how to spearfish. However he is overweight and cont hold his breath very long and its hard for him to snorkle. I cant afford one of those aqua lungs. and im not certified for diving so i cant get him gear. Any suggestions........