The right answers are: “A certain cool-headedness had come to him” and “doggedly he swam in that direction, swimming with slow, deliberate strokes, conserving his strength”. He is in a difficult situation, not the first time, because the lights of the yacht ended up markedly collapse and progressively vanishing fireflies; then they were cleaned out altogether by the night. Instead of crying and get mad to see if anybody could hear him, he decided to yell that is more effective because it makes more noise.