Possible Clues:

• Welsh root
• Sounds as if water may get through the back of the bottom of the ship
• Green vegetable
• Vegetable is large – it's frightening
• Vessel returns, displaying national emblem
• National symbol is close to bell with a frightening sound
• Veggie that looks like an overgrown scallion
• Sounds as if a vessel sprang such a hole vegetable in the bottom up here
• Cylindrical vegetable
• Vichyssoise onion