The lifeguard - Lycée de la Salle (Alès)

A lifeguard on the beach sees a victim in a calm water (lake/sea). We know the distance between the position of the lifeguard and the shore, his speed on the beach, and the distance between the point where the victim is and the shore, as well as the lifeguard's speed in the water. What is the fastest path of lifeguard to reach the victim?