There are plenty of places to swim in and around the CHillboro area.  Here are a few:

Chapel Hill Community Pool:

Very nice pool and its cheap.  Unfortunately it is under construction till sometime in mid to late 2007.

http://chapelhillparks.org/chcommcenterpool.php 

 CHillboro YMCA:

You have to be a member.  Nice pool although a bit warm.

http://www.chcymca.org/ 

 UNC Wellness Center in Meadowmont:

Very nice pool but costs an arm and a leg ($12) if your not a member.

http://www.uncwellness.com/ 

Meadowmont Outdoor Pool:

Not a great place for laps.  Its the outdoor community pool so its only usable when its warm and then you are competing with mobs of kids.  Not cheap either.  

http://www.meadowmont.com/inside.php?p=whatis/swim_club 

 UNC Pools (Bowman Grey):

 Nice if your affiliated with the University.  Otherwise....no dice.

http://www.aquatics.unc.edu/ 

UNC Natatorium:

I swim here with the UNC Master Team.  Very nice pool but very limited hours and is often closed for basketball games etc...  A word of caution - the website is very out of date.

http://www.ncaquaticmasters.org/masters.htm