There are only 2 ways to catch him. First, feed him and get him to come up close enough to grab him by the neck and wings (gently of course as you do not want to hurt him or get hurt). Using a net will be futile because if he sees it, he will not come back to you ever again.

The second way is to use a boat or kayak. Kayaks are great in that there is less noise and stress on the bird, but you will need 2-3 depending on the size of the lagoon and if there is a smaller channel you can get him into to corner him or at least run him on land into a pen, chute or other natural/man-made obstruction so that he cannot escape.

Using a kayak, is not going to be pleasant for the kayakers because they will probably get sewage on themselves and the top of the kayak. So, this may not be a great option unless this is reclaimed water which will be a little better than raw sewage.

If you use a boat, you will need an experienced boater who can turn on a dime without flipping the boat but will be able to stay behind the swan and keep him moving in one direction toward land or some physical obstruction for cornering. Usually, if the boater is slow and steady and can maintain a good distance from the swan, there will be no need for evasive action. You do not want the swan to see a group of people on the banks as it will double back.

Your land capturers or people capturing in a smaller channel need to stay out of sight until the swan can move into the capture area or he will avoid the area and the boater will be going round and round until the swan gets too tired. This is not good because the bird can become extremely stressed and in a sewer environment, you do not want him accidently inhaling sewage into his lungs.

Once you capture him, it would be a good idea to get him to a vet to make sure that he has no external wounds from being in the contaminated water and conduct a blood panel to insure that he is not septic internally from an infection from eating or swallowing sewage. Good luck. Please let us know the outcome. The Regal Swan