I feel your pain.... the last four times I've hunted... the birds have been on the other side of the swamp... whatever side I am on is always the wrong side... and the hens will be between me and the toms. So it goes.
It is fairly common place to call one out of the tree across a body of water. I wouldn't put money on calling one across once they are on the ground, but it does happen with relative frequency. Birds will often cross on their own. Keep in mind how nature works... the hens are usually the ones who fly across to the gobblers.... so if you get hot and heavy on the call... the bird will often just stand at waters edge and gobble like an idiot for 15 minutes before turning around and walking off when you are a no show.