The small, fast ones that show up when you've stopped looking.

Dolphins have a beak-like snout, a tall curved dorsal fin, and cone-shaped teeth. Porpoises have a blunt face, a small triangular dorsal fin, and flattened, spade-shaped teeth. They belong to separate families — they are not simply two names for the same animal.

Behaviour can help too. Atlantic white-sided dolphins are energetic and social, sometimes leaping, bow-riding, and splashing at the surface. Harbour porpoises are much more understated: they often roll quietly at the surface, show only a small triangle of fin, and disappear almost immediately.

Both species hunt small schooling fish and squid and use echolocation — rapid clicks that bounce off objects and return information about their surroundings and prey. Harbour porpoises produce extremely high-frequency clicks, reaching around 130 kHz, well above the range of human hearing.

Fundy's strong tidal currents and tidal fronts create productive feeding areas where prey can concentrate. Harbour porpoises are often associated with these productive coastal waters, including areas around Grand Manan, Head Harbour Passage, and the Digby Neck.