Pier Pressure is received in Act 1, after you have defeated enough Redwater Teeth at the Docks at night. It starts a quest with the same name.

Letter Edit

Directions to the Redwater Teeth Base

Keep your eyes inland. We got a new home here in the Docks, but Leech don't want no one to spoil it until we're in too deep to dig out. You know how he deals with people who try to take what's his. Here's the route. Don't overuse it.