I agree with bobad. The best thing to do is be careful and don't be foolish around ponds because there could always be a snake near it. Walk with your head down, use a walking stick in front of you and walk with heavy steps. The snake can't hear you, but it will fill your vibrations and try to escape the disturbance.
Try and learn to appreciate the animal. After all, one of the reasons people build ponds is to attract wildlife. Snakes are part of that wildlife and are actually rather entertaining to watch.
Get a book and understand what snakes you have and teach your kids about them. I find it wiser to teach kids to be careful and knowledgable about snakes, rather than training them to automatically react with a kill them mentallity.
If you do have poisonous snakes now, or in the future, then you would want to remove them. However, it is unlikely that's what you are seeing. It's very rare to come across a poisonous snake.
For ID purposes, poisonous snakes in the U.S. have cat like pupils in their eyes. They also have heat sensing pits in front of their eyes. Or, their coloring bands will tell you their poisonous. As for the mocassion, it will be rather short in comparison to its girth. They don't get very long, but they do get thick. When they swim, their entire body is on top of the water.
Like I suggested before, get a book and learn about them. It can be like birding, except you won't see near as many snakes as you do birds, which makes it more challenging and exciting.
