Stealth mode
Press C to crouch and enter Stealth Mode. A cyan ring marks the target pirate. When you get close, the prompt changes to "Stealth Take-down" with an Attack button. A loading screen tip says that when you crouch you can stealth takedown enemies.
Execute
After the Stealth Take-down, press V to execute the downed pirate and then pick up the bag. An Achievement Earned banner and Gained Utility and Discovered Utility notifications appeared during this sequence. A developer tip says you cannot stealth execute while in combat.
Takedown system
The on-screen action prompt changes to "Takedown" when a target can be taken down. The left HUD hint list showed Drop Strike, Takedown and Attack. A takedown can also be done from the air with Sea Flight, which gives a longer range than a ground takedown.
Hiding
A player can hide in a bush to avoid a pursuing Marine. The Marine searched for the player and walked past the bush without finding them.
Lock picking
Lock Picking is a short mini-game shown in a cage. The panel lists A for Pin Left and D for Pin Right. Rotate the tool until you see a green glow. When it is aligned, the lock glows green, bursts open, and the cage door swings open.