Related Clues:

• It makes a sound
• It has a floor but no ceiling
• Mermaid home
• Briny expanse
• Rivers' destination
• Atlantis cover, supposedly
• Crossing medium
• It has arms and waves
• Mariner's milieu
• Most of the Earth's surface
• Great expanse
• Briny deep
• Humpback's home
• Lighthouse view
• Plethora