I posted a map of the county I live in a while back to show how much water there is near me. A good percentage of the surface water around here is deep enough to swim in, and is generally clean enough that you don't have to worry about contracting diseases or chemical reactions if you get into it. Drinking it unfiltered would be unwise, but for recreational purposes it works just fine. We have several parks/lakes with swimming areas and a few municipal swimming pools, but a lot of people like to swim wherever they can get into the water. Leeches aren't much of a problem in flowing water, and they don't eat much anyway.
Walking into a lake after a day of heavy physical labor serves to cool the body and clean off the worst of the dust and debris that sticks to sweat. (Never dive into any body of water that you haven't checked for depth; I know of two people lucky enough to have survived doing so and they're both in wheelchairs for the rest of their lives. The human spine was not designed to take the impact of your body weight if your head hits the bottom of a shallow lake. Spinal injuries don't heal, and are often fatal.) Scrubbing the top layer of grime off in a lake or pond will reduce the amount of clean water that you'll need for hygiene purposes. As long as the weather and water temperatures allow, going swimming can reduce bathing without sacrificing hygiene.
Water conducts heat very well, so immersing your body in room-temperature water will feel a lot colder than the air above it. Cold water survival is another topic, but be aware that hypothermia can occur in cold water a lot faster than in air at the same temperature. Very rapid cooling of the body can also lead to cardiac shock (stuns the heart) in people with weak hearts or poor body temperature control, so avoid diving into that cold water if you're overheated.
Learn to Swim
Water isn't just for drinking or swimming, and knowing how to swim can become a life-saving skill if you have too much water. This is a skill that I consider so very basic that it gets overlooked. We're not born knowing how to swim, but the resources are available and it is something that everyone should know how to do. Almost every YMCA in the country offers swimming lessons for all ages, and the Red Cross can steer you towards other sources since they're the main certifying agency for swimming instructors. Cub/Boy Scouts also teach swimming as a basic skill; I'm not sure about the Girl Scouts.
Learn how to swim at whatever level you feel comfortable with: We're not looking to win an Iron Man competition, just being able to get ourselves out of a sticky situation. Hurricanes, flash floods, earthquakes, and various other disasters can create water hazards that you may have to deal with. If you don't know how to swim and get stuck in a flooded area, you're going to be the person being rescued by the National Guard on the nightly news.
It is my opinion that nobody should be allowed on a boat of any size, on any body of water, until they know the basics of how to keep themselves afloat; flotation devices are nice, but they have their limits and may not be available in every situation. Canoes and kayaks are fun, but they tend to tip over. Fishing boats can almost sink; they're built with flotation chambers in them so they won't go completely under unless they break up. Need I mention the Titanic?
Swimming is a stealth prep, something you can train on, practice, and learn without scaring the neighbors and have fun at the same time. Equipment costs are minimal (swim suits are sometimes optional) and it's a great way to unwind at the end of a day.