Here is the full list of all 18 Clean the Sea! achievements.
Sell 1 piece of junk
Sell 100 pieces of junk
Sell 200 pieces of junk
Sell 300 pieces of junk
Sell 400 pieces of junk
Sell 500 pieces of junk
Sell 600 pieces of junk
Sell 800 pieces of junk
Sell 1000 pieces of junk
Sell 1 piece of golden junk
Sell 10 pieces of golden junk
Sell 25 pieces of golden junk
Unlock 1 area
Unlock 5 areas
Clean the Antartica
Upgrade your boat
Upgrade your picker
Rent a drone