Background
Human beings in the World of Avatar learned the art of water bending from the Moon. How exactly that happened I'm not sure but that is how the legend goes.
Description
The northern and southern tribes and yes even the swamp tribe that produce the water benders are the World of Avatar's equivalent of our world's Inuit or Eskimo if you will but as a cultural note Inuit generally don't like being called Eskimos as it means "blubber eater" and is not the actual name of their people
Powers
Water benders use their chi to imitate the moon to push and pull on water. With training this becomes a complete art form that permits them to do all kinds of things far beyond just attracting and repelling water. All benders can do simple things like cause water to float up into the air or shape it into fluid forms like rings, whips and spheres. There is a long list of skills created to manipulate water in a variety of ways like creating water bullets or water running.
Aside from being able to simply move, shape and levitate water a water bender can alter its physical state by either freezing it or turning it into steam. Consequently they can also manipulate ice and steam as easily as they can manipulate water in its liquid state.
As with all bending techniques water bending requires the bender to be able to move in order to direct their chi to manipulate water. Although how much movement is needed is up for debate. Masters of great skill can actually manipulate their personal chi with very little need for movement. Although not a water bender King Bumi was able to use earth bending with just a simple head movement. He had no choice his body was restrained in an iron box. In a water bender's case the arms are the most important parts that needs to move.
A secondary skill with water bending that shows up from time to time is the ability to influence the chi in another living being's body causing accelerated healing when she (female water benders tend to be taught this skill or have a natural aptitude for it) covers the wound in water. This skill however can't cure birth defects or cause a subject's body to heal things that it couldn't naturally heal.
Water benders are strongest during the night of the full moon and powerless during a lunar eclipse. The new moon doesn't leave them powerless but they are definitely not at their most powerful then.
Other uniquely developed techniques include plant bending and blood bending. Plant bending works on bending the water inside a plant and blood bending is performed by bending the water found in blood. Unlike plant bending that can be used as long as water bending is possible blood bending can only be performed during a fool moon. Blood bending basically permits it's user to manipulate creatures with blood like puppets.
Water benders can draw water from virtually any source not just water that is obviously out in the open. A skilled water bender can draw water from the air (even when it's not raining or humid) and even from living beings. Katara used has used her own sweat.
How much water a bender can manipulate and how far away they can reach water from depends of their potential and training. Katara could manipulate enough water to separate the war ship she was standing on from another warship and even move it away from them.
If I Was A Water Bender
I live near a great lake and consequently a place with high precipitation. I wouldn't be at a loss for sources of water to manipulate. However I would still carry a water bottle with me or maybe a camel pack just to make sure I always have some.
Now if I were a water bender I would probably become a life guard. You know water bend the liquid out of the lungs of drowning victims, use water to lift people out of the water, or rescue people from undertow. You know let the water do the work that other life guards have to do manually.
I would also use water bending to cook. In more than one episode Katara has used it to stir and serve soup. You can do more than that however. With the power to alter the state of the water you could boil water without adding a fire or freeze it without using a freezer. Not only could you boil and steam food you can act as a living microwave over. Microwave ovens cook thing by heating up the water inside them. On top of that you can can also make frosty drinks and desserts. You could offer a full dinner. It might behoove me to expand my cooking repertoire and take up mixology so I could offer a complete restaurant service.
Since I live in the cold, cold north water bending offers me something else. One I don't need to buy snowshoes, skis or skates or even a snowmobile. I can use one of the many water bending techniques to travel along the snow and ice that covers the ground and water. Also I would never lack for anything to bend at that time. I think my winter would consist of doing two main things: shoveling driveways and roads; and ice sculpting. There would of course be other activities. I would make giant ice rinks for people to skate on during a winter festival but I'm sure I would be spending most of my winter making sure people weren't trapped in their homes and that emergency vehicles can get where they're needed.
Personally I'd use my bending to make sure that I always have a "sauna" or "hot spring" whenever the opportunity presents itself. I love how relaxing those are. I'd also buy myself a canoe that I can use to ride around in. Especially in the winter. I can see me sliding around on the snow doing my shopping. Then making my way to the river that divides the town in two and take off to my sister's cottage in a near by lake. For the first time in a while we would be able to keep it open year round.
I might also learn to build ice buildings like an ice hotel. If I did I know I would build myself an ice fortress during the winter and stay in there. Arm it with huge snow and ice balls. It would have many slides and doors only I could open.
Thanks for reading.
