For lap swimming, choose a watch with a compatible pool mode that counts turns and lets you set the pool length; for open water, look for a model with a GPS swim profile. Garmin says its pool distance calculation multiplies counted lengths by the pool size you enter, while GPS can be less accurate when the watch is repeatedly underwater. Check the exact model's activity list, pool-size options and metrics before buying.
Choose a pool-tracking watch for repeatable lap counts and a correctly set pool length. Choose an open-water model when you want a GPS activity, while allowing for route gaps when the watch goes underwater.
What changes between pool and open water?
| Use | What the watch needs | What to check |
|---|---|---|
| Lap pool | A compatible pool-swim activity and the pool length | Turn detection, length units, interval controls and the metrics you use |
| Open water | A compatible open-water activity with GPS | Satellite options, route recording, battery use and the maker’s accuracy guidance |
For Garmin’s Pool Swim profile, the watch detects completed lengths from movement and multiplies the count by the pool length you set. The support page lists 25 m, 50 m, 25 yd and other options, with custom lengths on compatible models. A wrong pool setting produces a wrong distance even if every turn is counted correctly.
Open-water GPS has a different limitation: GPS signals do not travel through water. Garmin notes that a wrist watch is repeatedly submerged during a stroke and recommends acquiring the satellite signal before entering the water. These are manufacturer-specific instructions, not a guarantee that every watch will record every route accurately.
Match the watch to your sessions
- Mostly lap swimming: Confirm the pool mode supports your pool length and whether it records the intervals, strokes or rest periods you care about.
- Mostly open water: Check for an explicit open-water profile and read the maker’s guidance on GPS acquisition and route accuracy.
- Both: Compare the activity list and battery details for the exact model. “Water resistant” by itself does not confirm that a watch has swim tracking.
- Triathlon training: Pair the device decision with swim wetsuit sizing and race temperature rules. For either setting, start with goggle fit and lens choice.
Sources
Common questions
Do swim watches use GPS in a pool?
Garmin's Pool Swim profile counts lengths from movement and uses a manually selected pool size. Other makers may handle indoor swim tracking differently, so check the watch's support page.
Does GPS work underwater for open-water swimming?
Garmin says GPS signals cannot travel through water, so a watch that is repeatedly submerged can have difficulty recording an accurate open-water route.
What pool size should I enter?
Set the exact length of the pool where you are swimming. Garmin lists standard options including 25 m, 50 m and 25 yd, and supports custom lengths on compatible watches.
Does every swim watch track pool and open-water swims?
No. Activity profiles and metrics vary by model. Confirm that the specific watch supports the pool or open-water mode you need.