It is getting hot in Texas....
Things change a lot here to "water sports" ....
With hundreds of miles of fantastic coastline, and hundreds of inland lakes, ponds, and rivers, Texas offers a visitors a variety of water sports to choose from. Whether it is a slow-tube down the Guadalupe, kayak or canoe down the Brazos River, or the hill country rivers, or riding a wave off South Padre, there are plenty of ways to "get wet" in Texas.
San Antoinio Dowtown River Area
For water sports enthusiasts, kayaking, boating, and tubing adventures are available on many of the state’s coastal and inland waterways. Texas’ top ranked water parks are open for business and thrilling kids of all ages. And visitors to Texas beaches can play in the surf, bask in the sun, or build a sand castle on miles of sunny beaches along the Texas Gulf Coast, from Galveston to South Padre Island.
Those preferring a more laid-back ride will find it at SeaWorld San Antonio’s new Castaway Cruisin’ attraction that will allow visitors to kick back for a smooth float along a 1,200-foot-long water route enhanced by tunnel jets, foam shooters, misters and rapids. The park’s hilarious sea lion stars Clyde and Seamore will also attempt to unravel the mystery of disappearing fish in “The Cannery Row Caper,” a new show styled like a 1930s detective film.
Gudalupe River:
The Guadalupe River provides exciting water recreation for visitors of all ages - from fly fishing to tube rides. The Guadalupe River, between Canyon Dam and New Braunfels, Texas, is famous for its exciting rapids, sparkling clear waters and water tubers. Meandering down this river in an inner tube is definitely a "Texas thing." I would visit the Hill Country, just to make sure I did not miss out on this unique experience. Guadalupe River State Park Tube Texas
Map
About.com Texas Travel has some great list:
Top Texas Water Sport Lakes
Natural Swiming Holes
Krause Springs Near Austin and here is another one close by
Hamilton Pool Preserve
Barton Springs Swimming Hole
This is an "Austin thing"... and remember Austin is "weird"... (with a smile)...be sure to go!
Lake Travis Lake Travis Near Austin
Summer Water Sports in Texas
Texas Lakes
Texas Surfing Options
Windsurfing
South Padre Island Diving
Galveston Kayak Tours
Lake Whitney State Park
Schlitterbahn Galveston Island (Water Park)
Dallas area is full of water parks, as is San Antoino, and many other places.
See the top 6 Water Parks in Texas list.

NRH20...North Richland Hills in Metro Area Directions
Of course, we could not forget the big summer event for thousands....
Six Flags Over Texas
Six FlagsFiesta Texas
Hurricane Harbor (Metro Area)
The coastal fishing is equal to any in the United States, the lakes such as Lake Fork continue to produce excellent trophy fish every year!
On Lake Fork Creek, lake's acreage is 27,690 at conservation level. Little clearing of timber was done prior to impoundment, making for excellent fish habitat.
Happy Water Days in Texas!