If the eggs are submerged under water, the chances of survival are diminished because the eggs are actually permeable (air can enter and exit). Submerged in water, the air would not be available and the young would not survive. The mother swan knows when eggs are not viable, not fertile, etc. Therefore, she will determine the eggs' viability and will leave the nest when there is no hope of anything hatching.

We are located in Florida, so we have no idea who might be responsible for cleaning and maintaining the sluice. You might contact your local city or county council or commission and see if they may help. Local water authorities, wildlife entities may also be able to help. The Regal Swan