Swimovate are the market leaders and have been selling PoolMate watches worldwide since 2007. Before they launched, the PoolMate had been extensively tested by a wide variety of swimmers over a 2 year period. They have a database of hundreds of kms of swimming and an accuracy rate of over 99.75%. There are tens of thousands of PoolMates being worn everyday and helping swimmers all over the world. The watch has full CE and FCC approvals. Patents and trademarks granted. As long as you have a regular stroke and take more than 7 strokes per lap (on the arm the watch is worn on) you should have accurate results.