Unlocked by

• Ravaging Dredge Harpoon Gun
• Rejuvenating Dredge Harpoon Gun
• Honed Dredge Harpoon Gun
• Strong Dredge Harpoon Gun
• Vigorous Dredge Harpoon Gun
• Hearty Dredge Harpoon Gun
• Hunter's Dredge Harpoon Gun