It is always sad to loose a fellow spearo. The most common cause of death after shark attacks is bloodloss, especially with upperleg wounds. I urge everybody to watch this link(my abilities did not allow me to post the clip directly). This is the best equipment you can have to save you buddy's life.
www.youtube.com/XSiwYZ-Vvs
www.youtube.com/XSiwYZ-Vvs