The tag doesn't give any dat during the swim, just a red flashing LED that presumably indicate that it's working. After the swim when you return the watch to the attendant the swim data is uploaded and processed in the the cloud into a swim.
You can only register after your first swim, I suppose to ensure that registrant must go to a participating pool. It's also possible to set up an auto upload to Strava. This is a bit limited as only total dat is sen, not detail of sets. Whilst we're on sets, these are detected automatically based on a pause in rhythmic swimming.
The image above shows how short pauses are identified as a single length and a longer pause as a 'set'. There are no buttons on the tag to record anything. This view shows the 'editor' that allows users to merge or split lengths that have been incorrectly defined by the software. Unfortunately there doesn't seem to be a way to define a set manually.
My swims have been at a spread (slow) paces and with a gradual loss of technique. I've had to slow down during a length ad occasionally had to do a few strokes of breaststroke to stay behind in a lane. All of these variations have been recorded accurately.
Naturally SWIMTAG has a plethora of social media features including friends, virtual races and challenges.
Overall the key part of the system, that is swim tracking, seems more reliable than the Garmin Swim and the online processing a clever way to be able to update the analysis algorithm without troubling the pool staff.
