Believe it or not, a Big Daddy is simply a human being that has been steam-sealed into a massive deep sea diving suit. These entities were first conceived by Dr. Yi Suchong and then given the green light by Andrew Ryan. Realizing that the Little Sisters being sent out to harvest Adam would be quite vulnerable, they decided to permanently fuse human candidates (willing or unwilling) into these suits, inject them full of strength-enhancing plasmids, and then train them to protect the Little Sisters at all costs. If you want the Adam being carried by a Little Sister, you're going to have to deal with her Big Daddy protector first.

Rosies are the ranged version of the Big Daddy and can be encountered in both standard and Elite versions. Both versions are armed with a Rivet Gun that fires high-velocity rounds capable of inflicting massive damage. To further aid in the elimination of any perceived threats, they will also toss out Proximity Mines. When battling one, keep your distance and avoid treading the same ground twice.

There are five research levels that can be attained by snapping photos of Rosies or Elite Rosies:

• Research Level 1: Increased Damage (+)
• Research Level 2: Photographer's Eye 2
• Research Level 3: Increased Damage (++)
• Research Level 4: Rosie drops almost always contain rare invention parts.
• Research Level 5: Increased Damage (+++)