The aquarium opened in 1969, housing an orca named Haida which had been captured in 1968. Shortly afterwards, the aquarium decided to capture a mate for him, taking a partial albino named Chimo. She died in 1972, a little over 2 years after her capture; the disease which caused her albinism, Chédiak–Higashi syndrome, made her very susceptible to illness. Haida, her mate, mourned her death, and remained alone for years . Eventually, Sealand captured a female whale named Nootka II for his mate. Nootka II, however, died after 9 months. His third mate, Nootka III, was also short-lived. By the time of the death of his third mate, Haida displayed no interest in them.
In 1977, Sealand captured a young orca which was found alone, emaciated, and suffering from bullet wounds. Miracle became a popular attraction, but was kept in a separate pen from Haida. Several years later her companion in the pen, a seal named Shadow, drowned in the nets forming the pen.
As anti-captivity protests began to put pressure on aquariums, Sealand agreed to release Haida, but the animal died a few days before its scheduled release in October 1982, with no evidence of foul play . His release had been part for the aquarium to acquire new whales. Many people were outraged by the plan of capturing more whales, and staked a protest at the supposed capture site. Sealand soon obtained three whales captured from Iceland.
The three new orcas, Tilikum, Nootka IV, and Haida II, never had good dynamics together, and indeed, the male Tilikum was often bullied and chased into the medical pen by the two females.