Possible Clues:

• Recedes to the ocean
• Goes out after a rise
• Draws back, as water from a beach
• Moves like the tide, sometimes
• Loses strength
• What this does after it's tied up, by the sound of it
• The turn of 31 across goes out like this
• Flows the other way
• Guest-house in centre of Tresco is declining
• Is refluent