I don't have the Garmin Swim yet, but have a question:
When you reach the wall and stop swimming, does the watch stop the time for the length or is the time running on, counting this as a very slow length?
I have found that trying to race to press the pause button as quickly as possible has caused me to inadvertently hit the stop, rather than the pause button. If you do this you lose the last session data of your swim -- or I did anyway -- so be careful ensuring you press the correct button! Anyway, you're only shaving off fractions of a second and you'd be cursing yourself if you're finishing a big swim and you lose data for want of adding a second or two to your total pool time!.
Have to say that sounds a bit crazy!
The idea of stopping every 25 meters to pause then un-pause between each length is not, I suspect, how the designers of the watch intended it to be used :)
Still, if it works for you !!!
Ralph