What is the best way to create a boggy pond for wildlife?

I live in Berkshire, UK, and my mother in law would love to have a boggy bit of the garden to encourage different types of wildlife. Does anyone have any pointer/tips on how to create a small area like this, and also any advice on how to make sure the dogs don't interfere?What is the best way to create a boggy pond for wildlife?
this is what I would suggest you doing. clear the spot you want to put the bog. dig it down about 6 inches or so and lay down a chunk of plastic or tarp that will be bigger then the area you have for the bog. if you want the water to be filtered use a pump under the rocks this will also help the water to stay fresh for the critters that enjoy the pond. you will need what I call river rock which is a colorful rock that can be of any size. lay this down on the liner and then start filling the bog with water, the water an be over the rocks as some evaporation will occur as the sun and wind will absorb it. as far as dogs bothering the pond I use to have that problem but they soon lost interest in it.you could put water somewhere else so as they won't bother your pond. have fun with what ever you do.