A decent stopwatch (watch)

Looking for a convienient stopwatch that I can wear (wristwatch) while swimming to accurately self time certain efforts. Something I can hit the "stop" button easily and consistantly in same amount of time following a finish. Basically just need a self timing instrument I can use to employ a method of maintaining an accuracy of at least 0.5 seconds human error (i.e. press "start", push off wall and swim, touch wall and press "stop"). If that makes sense. and not cost an arm or a leg. Thank you