I swim a mile 3x/week.  Low cost and worked well for 7 months but it is now rusted over and doesn't work anymore without pushing AND pulling on counter.  If you buy this, take care of it better than I did being sure to dry afterwards and that might prolong use.  Going to try the plastic finger counter to avoid rusting and having to stop every few laps to update counter.

I purchased this counter to keep track of my daily work out in the pool.  It is inexpensive and works perfect for the task.