It’s easier for most swimmers to sneak a look at a pace clock in the middle of a rep than it is to read a time on a watch, which is important if you want to check pace midway through a longish rep (ie. 300+ yd/m) or know enough pace clock math to be able to check distance traveled if you lose track of a lap count.
Ah, well I have a really good technique for that with my watch, I’m able to glance at it on the first arm pull after a turn, and I know if I subtract 2 seconds, that was my time at the turn. I have to modify my arm pull slightly to do this, but I reckon I lose very little time indeed. However many other people I know who wear watches are unable to master this technique. If I’m swimming 800m+ in one go, I’ll even push the lap button just before I turn at each 200m, do a double arm tumble, and glance at the split on the way out, that way I have a record of my splits after the session.
Just one thing to note about getting used to wearing a watch, though. If you ever take part in a masters swim meet, don’t forget to take it off to race, or you will be disqualified, as it is against the rules to use any device that can help with pacing.