I don't know if FW2.90 fixed it, or slightly changing my style did, but I now get consistently accurate lap totals. Yippee. But, it still uses a lot of battery. 15% drop in 30 minutes of continuous swimming. Worse than when running with GPS on for an hour. Also, the water contacting the face is activating unintended touch functions. At the end of a swim, the watch "settings" screen is displayed. Swiping it reveals the watch face. Then pressing the button seems to get it back to swim mode where another push stops the activity. Ridiculous. Water contact should not be activating the watch face. Perhaps Garmin should inhibit the touch screen function while swimming. (Garmin, are you listening?)
Are people swimming at night to need s back light? Garmin, fix this.