"It was absolutely dark and absolutely silent, save for the chattering of Phil's teeth. The ocean was a flat calm. A rough, rasping tremor ran through the men. The sharks were rubbing their backs along the raft bottoms." (Hillenbrand 129 )
Talking is more than just talking. It can help people through rough times. Louie and Phil had conversations that pulled "them out of their suffering". They'd make plans and had hope that they'd survive.
A moment that changed the course of the story was Mac eating the chocolate. Mac left "no chocolate" and "no wrappers" (Hillenbrand 132). The absence of the calorie filled chocolate ensured that their survival was going to be harder than expected.