Possible Clues:

• Sea with much floating weed
• 'Sea in the North Atlantic, the only sea without shores (8)'
• So a grass can be all at sea
• Sea whence eels migrate
• Atlantic sea surrounded by ocean currents
• So, a grass can make a sea?
• So a grass may be a 14 down
• Sea, weedy part of the Atlantic
• Seaweed and rags recycled, as in the manner indicated
• Sea noted for seaweed and eels