Dolphins rely heavily on sound production and reception to navigate, communicate, hunt, and avoid predators in dark or limited vision waters. This is why they are greatly affected by noisy activity at sea. There are many situations where warning of the presence of dolphins is required, mainly to protect the dolphins from harm, for example during seismic surveys at sea, or during operations in military firing and bombing ranges. Together with sound engineers from Ultra Electronics Sonar Systems, we developed a new dolphin whistle detector algorithm that allows to detect the presence of dolphins using passive acoustic monitoring. This talk will give a short introduction to bioacoustics, will give an idea about how PDE theory and image processing can be used to protect dolphins and whales, and of course there will be dolphin sounds.