My first water garden was a container water garden—a large fiberglass pot filled with water and five 1-gallon pots of plants. Since then, I've graduated to a 4-foot cattle trough with an assortment of water plants staged on bricks stacked at different heights.
Seattle landscape architect Keith Geller likes to fill large ceramic containers with water, which he places to mark the entry into a new garden room. Often, they'll include small floating plants for added interest.
Basically, anything that holds water is fair game for a container water garden. It can be small enough to sit on a tabletop or as big as a barrel or trough. The secret is to find a pot without holes in the bottom, or to plug any holes so the water won't drain out. Add some plants, and some fish, too, if you like. If you want the sound of trickling water, place a small, submersible pump in the bottom of your container. These are low-voltage, waterproof units, and all you have to do is plug them into a nearby outlet. They recycle water through the pump and through a "jet" tube that can be topped with various heads for different fountain effects.