GamesRadar: How did the Big Daddy end up in a diving suit?

HP: We'd been thinking about submarines and bathyspheres for so long. Those diving suits were just so huge and intimidating that it was an ideal aesthetic for the character. Actually, there are two points in the game where you can see a Big Daddy walking on the ocean floor outside. They're hard to catch, but they're both in the Neptune's Bounty fisheries. If you stand in the basement under the tavern for five minutes, by the windows that bulge out, you'll see one stomp by in slow motion, with clouds of sand coming off his boots.

But we didn't set out to make the game with the Little Sisters and Big Daddies in mind. They were just ecological considerations - we wanted a small, helpless thing that carried a lot of resources and then we wanted a big and benign person to guard the resource carrier. After a while, we realized that we wanted the player to have more of an emotional connection with those characters, so they evolved.