Must have

• Ambient sound
  • Under water
  • Inside the ship
  • Outside of the ship
• Creaking floor boards
• Footsteps
• Bubbles for the player
• Door opening and closing
• Crate pushing

Should have

• Crashing and breaking of objects
• Waves against the hull
• Passing fish “whoosh” sound
• Unlocking/Discovering sound

Could have

Would have