While a garden pond is perhaps the ideal form of water garden, it is perfectly possible for a miniature version to be built in a tub. This is the answer for anyone who only has a small garden or even just a balcony.
You can still enjoy the sight and fragrance of the water lily and even a few fish. This article by Beckie Fox which I found on the Canadian Gardening website explains how to construct your pond in a pot.

Making a water garden doesn’t have to require an engineering degree, a backhoe and lots of space. With a large watertight container and a minimum of six hours of sun, you can nurture a small collection of aquatics in a tiny townhouse garden, on a patio or even on a balcony. Best of all, you’ll be able to watch the sunlight sparkle on the surface of your pond in a pot with just a small amount of set-up time.

Putting it together
? Place the empty mini-pond in its intended spot ? once filled with water, it will be heavy and awkward to move. (A note to high-rise gardeners: just four litres of water weighs about four kilograms. Check that your balcony can support the weight.) Level container.
? Fill with water and let the container sit for one or two days to allow water to warm to ambient temperature.
? Submerge marginal plants to bottom of container; if necessary, place a brick or two on the bottom to raise potted water plants to correct level. Cover soil surface of each pot with a layer of coarse or pea gravel to keep soil in place.
? Add floating plants.

See more at Canadian Gardening
Image source: Linda N