Porpoises swim in the Oosterschelde, the most common cetacean in our coastal waters. At Serooskerke you look out over the water where they swim. Usually you will see a dark back with a small triangular fin roll briefly above the surface and vanish again: a porpoise does not jump like a dolphin. On a calm day with little wind and few waves your chances are best. Bring binoculars and be patient.