Garmin 245 Music Pool Swim not registering all laps

Hi using the Garmin 245 Music for pool swim and its just not recording correctly.  I swim continually without stopping but when i look at the activity it looks like i have stopped on several occasions and no laps registered.  Quite frustrating, am i doing something wrong.  Out of the last 5 swim only 2 of the 5 have recorded correctly.  This morning i was missing about 200m-300m from my swim.