You make a big tank on land and build a sort of canal from the sea to the tank. Then you get on a boat, find a whale and bring it back to land by hitting it by your bare hands and making it follow you. Bring it to the tank through the canal and presto, you have a whale!
I remember years and years ago, when I was 4 or 5, I had a pet beluga whale named flower. She had the biggest tank ever, and I mean BIG! It was the size of a large island! Still, since I was young, I had loved sea world, so I built a glass platform above the water so I could stand and watch her. Somehow, when I was getting more food from my inventory, she glitched into the middle, and by the time I got her back into the water, she was dead. I’m trying to get another beluga so I can give at least another a better life. RIP Flower, 2010-2010.