I live in an extremely rural area. The local health club, complete with 1 treadmill, 1 elliptical, and a bow flex, also has an endless pool.  I have really come to appreciate this pool, at the beginning of training I swam like a rock!! But now because of the privacy of the endless pool i have become much more relaxed and have really gotten to work on my stroke.  Problem is, I have no clue how far I am going.  i have worked up to where I can swim for 5 min w/o stopping, but don't know how far that really is, or how long it should take to swim the 1/2 mile sprint. 

Any details for me??