Some beach buildings can only be unlocked in order, while others require Golden Keys. Golden Keys can be obtained by through Shipment or Disaster Challenges. Shipment Challenges become available when your population reaches 20,000 Sims and you have the Cargo Ship Dock. You must fill specific orders for Sims and produce goods for them, which earns you a Golden Key per filled set. Disaster Challenges require Dr. Vu's tower, which becomes available when your population reaches 90,000 Sims and you have 60,000 Simoleons. Bring Dr. Vu certain items so that he can unleash disasters. You must then repair the damage he causes. You will earn two or three Golden Keys for each building repaired.