Sea Monkeys or Brine Shrimp? And how do we take care of it?

My sister just came home holding a water bottle with a little whiteish opaque ball in it. I asked her what it was and she said, "Sea Monkeys". Sea monkeys are also known as brine shrimp, right? So I think it's a toy, but she says it's real. It looks an awful lot like an actual egg sac, so how do we hatch it? And what do we feed them?