The bodies of water in Tampa are actually mostly swampland, but luckily, there are several really gorgeous beaches that are within an hour's drive away!  Here are my favorites:

• Clearwater Beach -- beautiful white, powdery sand on a big beach!  There's a little hut on the beach that sells cocktails, several restaurants that line it (I dig Frenchy's Rockaway Grill!), people to rent lounge chairs, umbrellas, and water sporting equipment from, and then some.  Make sure you bring cash to this one because sometimes when it's busy, you have to pay for parking, and also, you might be tempted to grab some food!
• St. Petersburg Beach -- this is like the less happenin' version of Clearwater Beach.  Less people, which is great if that's what you're going for, and it also makes it easier to find parking.  I prefer the offerings of Clearwater Beach sometimes, though, in terms of dining options and businesses on the beach.
  
• Sunset Beach -- my favorite part of Treasure Island to visit is Sunset Beach, particularly the restaurant Caddy's On The Beach!  It was recommended to me by a waitress in Tampa.  The restaurant is right on the beach front and you can order food and drinks and bring it onto the beach.  You can also tip some hot beach bodies they've employed to set up lounge chairs and umbrellas for you.  One time, I saw a manatee swim up here!
  
• Indian Rocks Beach --  this is a small, quiet beach as Indian Rocks is more of a retirement town than anything.  Great to wade in the water and then relax and read a book on the sand.  Also nice to walk on the street that the beach is on and stop by the little businesses.  I love Indian Shores Coffee Company for coffee and lighter snacks and Mahuffer's is a, um, real hoot, if you're looking for a drink (you have to at least check out the outside decor!)
  

If those aren't enough for you, here's a list that has a few more beaches on a Tampa tourism site.

Have fun! :)

Saint Pete Beach is the best option in the Tampa Bay area. Try Postcard Inn as a hip place to hang out. Clearwater Beach is very touristy and all the other Tampa Bay beaches are nice --- but not incredible. I would also HIGHLY recommend Siesta Key, which is an hour south of Tampa --- maybe a little less from St. Pete. Best sunsets on the Gulf of Mexico and great beaches. 

The beaches in tampa are on the bay and not very nice. go any where on the gulf.  Honeymoon Island State Park is supposed to have one of the best beaches.  Clearwater Beach is the most popular

Clearwater Beach is the main big popular beach in the area but can get very crowded. Clearwater Beach has a great sunset festival. If you're looking for a gorgeous beach check out Caladesi Island You'll need to go to Honeymoon Island State Park and take the ferry across. Also Fort Desoto State Park And Beach is one the top beaches in America. It's only about 45 minutes from Tampa

Indian Rocks Beach is awesome and mostly quiet. If you go be sure to check out Keegan's Seafood Grille