When I first started at Sealand, every evening all three of the killer whales would be put into the module to be secured for the night. Coming from a farming background this at the time seemed similar in nature as putting cows back into the barn or horses into their stalls. The whales would go in, finish their daily food intake and let out back in the morning, with little or no difficulty.
Months later breeding activity intensified and the whales started to refuse to enter the module. At first simple deployment of the net in the main sea pen would work to put the whales into the module. Then the whales started to learn to lift up the net and what use to take a simple hand command ended up in a long extensive project deploying and redeploying the nets.
We consulted with the owner of the park and shared with him our concern on continuing housing all three whales in the module. One, because of the difficulty of putting them in but more importantly we could see the social relations intensifying between the animals. This was due to the fact that the two females were pregnant. Being able to breed animals is used by many captive facilities as a sign that their operations are working. So despite all three whales being "locked-up" in the module nightly for years, the pod of three successfully bred. The owner agreed to allow us to put only Tilikum at night with the theory the females would stick around if they somehow escaped from the main sea pen. In my mind, it was a good start as one in the module at night was better than three.