Possible Clues:

• Time-saver with locks
• Is a half-century able to make this in a panama?
• Cut through Panama
• Is a half-century able to hold water this way?
• Is a half-century enough to be able to dig it?
• Lake-to-lake link
• Manmade flower constructed from tin and aluminium
• Artificial waterway for barges
• Waterway with 39-Across
• Rialto Bridge sight