Little Sister Encounter
Big Daddy: Bouncer
Atlas radios you to warn of the Big Daddy and Little Sister up ahead in the Foyer. This is your first encounter with a living, breathing Bouncer so take a moment to top off your health and EVE levels and equip whatever weapon you have the most Armor-Piercing rounds for.
Before you can worry about harvesting or rescuing the Little Sister, you must get past the Bouncer protecting her. Use Electro Bolt to temporarily stun it, then open fire with the Armor-Piercing bullets. The Bouncer will not fire at you from a distance, but instead speeds towards your position and tries to drill into your body with its massive mechanical arm. Having the Static Discharge tonic equipped helps to knock it back and stun it when it does do so, effectively buying you some time to run. Try to keep as much distance between you and the Bouncer as possible and continue to use a combination of Electro Bolt and Armor-Piercing bullets to drop it.
Take the money from the Bouncer and do what you like with the Little Sister. Head back to the Gatherer’s Garden in the Lounge for a quick pit-stop and purchase the Enrage plasmid—it should come in handy early on in Neptune’s Bounty—and any other upgrades you can afford. Continue back through the Foyer to Emergency Access. Climb the stairs and use Dr. Steinman’s key to unlock the gate and board the Bathysphere.