Water makes a charming feature in almost any garden. But a fine setting will bring even greater beauty. If a well-planted bog comes up to the pond edge and reflects on the surface, that scene is perfected.
Natural bogs have a high water table or poor drainage. You can mimic that in a garden by laying a water-obstructing membrane below the topsoil. But the aim is to hamper drainage, rather than create a stagnant quagmire.