James,
Here is a suggestion. Build yourself or purchase a simple blind. Leave it in place for the entire season. I bought one for about $50 from Bass Pro, camo, one person, place to sit and watch. The water turkeys are one of the smartest birds you will ever run into, and at the same time dumbest. If they can not see your face, you are not there. If you are not there, they will land right in front of you and also eat right in front of you. When startled, they refuse to believe you are there and will fly right back to you to convince themselves they were right....until they see your face, then and only then, they will turn away.
Leave the blind in place and eventually they will associate bad things come from that blind and that pond may not be the most pleasant place to visit.
I can't overempahsize enough the importance of watching for and discouraging the scout birds. I wasn't kidding when I said they kiss and tell...they also report violent incidents to their buddies and share preferred sites. Don't believe me? Well, it's true. Those scout birds are the key. Teach them a lesson, even let them return to their buddies with some buck shot ringing in their ears and you will significantly reduce your problems.
My problem is that the scout birds find my pond while I'm not there...and then its Katy bar the door, party on!
p.s. the shotgun is much more terrifying to them than a far off rifle shot...get the biggest meanest, loudest gun you can and let them see and hear it in action.
