When Marineland Canada, located in Niagara Falls, Ontario, closed in September 2024, it left behind 30 belugas and four dolphins without a regular income to support their care. To ensure the animals’ well-being, the Association of Zoos and Aquariums coordinated an international effort to relocate them to the United States and Spain. After the move, one resident beluga and three transplanted belugas died at a U.S. facility, while one beluga died at a Spanish facility. Supporters of whale sanctuaries suggested that the Canadian belugas be placed in netted ocean pens, arguing that these environments are more suitable for the animals. A cetacean sanctuary is a large, ocean net enclosure that provides a habitat for marine mammals like whales and dolphins. These sanctuaries are guided by a philosophy that emphasizes no breeding, limited human interaction, and nonprofit funding. However, no active cetacean sanctuaries currently exist that fully meet these standards. In some cases, sanctuaries could offer a safe home for animals that are at risk in the wild while allowing them some level of autonomy. But for animals that have never experienced the open ocean, a sanctuary may not be the best option. What is natural for wild cetaceans may not be natural for those raised in human care. The word “sanctuary” may sound appealing, but it still represents a form of captivity. Releasing animals into the wild is often illegal for those currently in human care. In a sanctuary, animals remain behind nets and rely on humans for food and medical care. Managers must control the animals’ social groups, monitor their health, and respond to environmental threats. Moving a cetacean that has been raised in captivity into an unfamiliar sea pen can lead to various challenges. Historically, cetacean sanctuaries have struggled to get off the ground. The Whale Sanctuary Project in Nova Scotia, Canada, is still trying to raise funds and has not yet built its 100-acre sea pen. The National Aquarium in Baltimore, which had promised to move its animals to a sanctuary about 10 years ago, has not yet done so. Dolphin Project founder Ric O'Barry’s sanctuary in Bali, Indonesia, attempted to house four animals from a hotel but saw two deaths, one shortly after arrival and another during a release attempt. The SEA LIFE Trust Beluga Whale Sanctuary in Iceland has tried to relocate two belugas from a Chinese aquarium, but a 2025 review found that the whales spent most of their time in a conventional indoor pool instead of the sanctuary. In the sanctuary, they exhibited stress behaviors and had feeding difficulties, with one developing ulcers. These examples do not prove that sanctuaries cannot work, but they show that creating and managing these enclosures is challenging. They also highlight that animals may not adapt easily to new environments. Animal welfare depends on many factors, including health, social relationships, nutrition, the ability to make choices about how they spend their time, cognitive stimulation, and environmental predictability. Animals need enough change to stay engaged, but not so much that it causes harmful stress. The Cetacean Welfare Study provides a useful example of how scientific data can guide management decisions. Researchers examined which environmental and management factors are linked to better animal well-being. They measured how active the animals were, how they used their habitats, and the variety of behaviors they exhibited. They also analyzed stress hormones and other biological indicators. The study included over 200 individual animals across three species in 43 accredited zoos and aquariums. It found that the size of the habitat did not necessarily predict good welfare. Instead, the social environment, training, habitat access, and enrichment approaches were more important indicators. Each cetacean is unique. A 60-year-old wild-caught orca, an 8-year-old stranded dolphin, and a rescued newborn beluga likely require different welfare strategies. Best practices suggest that decisions should be based on individual assessments. Before a non-emergency transfer, professionals establish the animal’s baseline health, behavior, relationships, and stress levels, then track those metrics afterward. If welfare improves, the data should show it. If it declines, professionals can adjust their approach. The failure of the belugas in Iceland to adapt to their new environment suggests that future sanctuary plans should include emergency pools, allowing managers to move animals if problems arise or if stress levels rise. Sanctuaries can offer an alternative for rescued animals, but to be effective long-term, managers must follow scientific guidelines. Even before construction begins, managers can test protocols for introducing animals to these habitats and understand their space preferences. If sanctuaries have clear metrics for success, the public, researchers, and accreditation groups can track their progress toward improving animal welfare. These data, if made public, would be valuable for scientists. Keeping marine animals in sanctuaries is also more expensive than housing them in pools. For example, the orca from the film Free Willy, known as Keiko, required about $20–$30 million over five years for sea-pen housing. These examples show that sanctuaries need long-term funding and viable revenue streams before construction begins. Sanctuaries, as a concept, are neither inherently good nor bad. Like any animal welfare initiative, proponents must prove that they can work effectively.