The Killer whale is arguably the most spectacular animal to be found in or around Ireland. The male has true whale proportions, being up to 30ft (9m) long with a 6ft (2m) high dorsal fin giving the animal an unmistakable and decidedly sinister shape in the water. The female is only about half this size and the dorsal fin is much shorter and curved back, dolphin-style. Both are very strongly patterned; black above, white below, the white extending onto the sides in a wavy patch. There is another oval-shaped white patch above the eye on both sides of the head. These white patches and the large dorsal fins show clearly as the animals break the surface of the sea for a breath of fresh air.

Killer whales are sometimes seen alone but they often turn up in small groups (which may be family groups, often containing bulls, cows and calves) which hunt as a pack. They prey on seals, porpoises, dolphins and large fish including salmon. Despite their blood-thirsty reputation in the wild they can be tamed like dolphins and exhibit the same gentleness and intelligence in aquarium conditions. They are popularly featured giving 'piggy-back' rides to fearless handlers.

In the wild, Killer whales are found mainly in the seas above the Arctic circle. They do not reach maturity until they are about ten years old and they reproduce at a very slow rate - only one calf is born over a period of a few years. In autumn family packs follow migrating salmon to warmer waters and it is at this time that most are seen in Irish waters. They are annual visitors off the south and west coasts of Ireland. Regular sightings are to be had off Cape Clear Island in Co. Cork, sometimes at close range.

These whales communicate with each other underwater with a series of squeaks and other noises which facilitate navigation through inshore waters bringing them occasionally into estuaries and inlets. Despite the sophistication of their sonar equipment the odd one (as with other whales) becomes stranded in shallow water. In 1977 a Killer whale nick-named 'Dopey Dick' thrilled citizens of Derry by showing itself for a few days on the River Foyle before making its escape out to sea again.