My vivoactive 5 swimming is top right button short press (activities) scroll tap swim. Top right to start. Screen shows only interval time and distance or laps (configurable). Bottom goes to interval rest. Lots more data and a rest timer. Bottom starts swimming again. Top stops the activity. Long press top to save, bottom to discard.

All operations are buttons because the touch doesn't work well with water on basically every device.

Literally 3 clicks to a large lap counter.