In Nancy Drew: Sea of Darkness, Nancy wants to snoop through Dagny’s phone. To find it, you first need to help Soren with the rope/knot tying puzzle. Under the display is a note that says “Gunpowder.”
Follow this clue to the ship and down to the hold where the barrels for gunpowder are located. Open one of them to find a note left by Dagny.
On this note it mentions her phone password. Type in ‘Scuttlebutt’ into her phone to unlock it.