I like to call swampy areas/creek bottoms too.
Normally, I like to find a stump or brush pile I can climb on (to get a better view). MOST of the time, I hear them before I see them...pay attention to the squirrels chirping. Often times they have tipped me off that something is coming in.
Here is a pic of where I was calling last spring bear season, I was about 15 ft off the ground on an old stump. The trees were about 20ft all or more/brush was thick. This yote came in about 3 minutes (you could hear him)...had something else coming on the other side too, but I shot the yote first. I havent called in a ton, but I have got a few to show themselves.
Yote was like 20 yards or less away when I shot. This was just on the border of a swamp.
Good luck and dont give up. You never know what your gonna get!