Swim-app stops when submerged

import Toybox.Application;
import Toybox.Lang;
import Toybox.WatchUi;
import Toybox.Time;
import Toybox.System;
import Toybox.Graphics;
import Toybox.Time.Gregorian;

public var _lap0 = 0;
public var _tim1, _tim1a, _tim2, _tim2a;

public function toHMS(secs) {
    var hr = secs/3600;
    var min = (secs-(hr*3600))/60;
    var sec = secs%60;
   	var ret=min.format("%02d")+":"+sec.format("%02d");
   	if(hr!=0) {ret=hr.format("%d")+":"+ret;}
   	return ret;
}

class LapSwim1App extends Application.AppBase {
    function initialize() {AppBase.initialize();}

    // onStart() is called on application start up
    function onStart(state as Dictionary?) as Void {
        System.println("SwimApp started");
        _tim1 = Time.now();
        _tim1a = new Time.Duration(0);
        _tim2 = _tim1;
        _tim2a = _tim1a;
    }

    // onStop() is called when your application is exiting
    function onStop(state as Dictionary?) as Void {
        System.println("SwimApp stopped");
    }

    // Return the initial view of your application here
    function getInitialView() as [Views] or [Views, InputDelegates] {
        return [ new LapSwim1View(), new LapSwim1Delegate() ];
    }
}

function getApp() as LapSwim1App {
    return Application.getApp() as LapSwim1App;
}

class LapSwim1View extends WatchUi.View {
    public var _lap1 = 0;

    function initialize() {View.initialize();}

    // Load your resources here
    function onLayout(dc as Dc) as Void {
        setLayout(Rez.Layouts.MainLayout(dc));
    }

    // Called when this View is brought to the foreground.
    // Restore the state of this View and prepare it to be shown.
    // This includes loading resources into memory.
    function onShow() as Void {}

    // Update the view
    public function onUpdate(dc as Dc) as Void {
        dc.setColor(Graphics.COLOR_BLACK, Graphics.COLOR_BLACK);
        dc.clear();
        dc.setColor(Graphics.COLOR_WHITE, Graphics.COLOR_TRANSPARENT);
        var x1 = dc.getWidth() / 2;
        var y1 = (dc.getHeight() / 2) - 50;
        var delta_y = 100;
        var just1 = Graphics.TEXT_JUSTIFY_CENTER;
        var font1 = Graphics.FONT_NUMBER_THAI_HOT;
        dc.drawText(x1, y1 - delta_y, font1, toHMS(_tim2a.value()), just1);
        dc.drawText(x1, y1, font1, toHMS(_tim1a.value()), just1);
        dc.drawText(x1, y1 + delta_y, font1, _lap0, just1);
    }

    // Called when this View is removed from the screen.
    // Save the state of this View here.
    // This includes freeing resources from memory.
    function onHide() as Void {}
}

class LapSwim1MenuDelegate extends WatchUi.MenuInputDelegate {
    function initialize() {MenuInputDelegate.initialize();}
    function onMenuItem(item as Symbol) as Void {}
}

class LapSwim1Delegate extends WatchUi.BehaviorDelegate {
    function initialize() {BehaviorDelegate.initialize();}
    
    function NewLap() {
        _lap0++;
        _tim1a = _tim1.subtract(Time.now());
        _tim2a = _tim2.subtract(Time.now());
        _tim1 = Time.now();
        WatchUi.requestUpdate();
    }

    function onKey(keyEvent) {
        // 4 = top key , 5 = bottom key
        System.println("onKey: " + keyEvent.getKey() + " " +
          keyEvent.getType() + " " + _lap0);
        if (keyEvent.getKey() == 4) {NewLap();}
        if (keyEvent.getKey() == 5) {System.exit();}
        return true;
    }

    function onTap(clickEvent) {
        System.println("onTap: "
          + clickEvent.getType() + " " +
          + clickEvent.getCoordinates());
        if (clickEvent.getCoordinates()[1] < 200) {
            NewLap(); // Top half of screen
        } else {
            System.exit(); // Bottom half of screen
        }
        return true;
    }

    function onMenu() as Boolean {
        System.println("onMenu started");
        WatchUi.pushView(
            new Rez.Menus.MainMenu(), 
            new LapSwim1MenuDelegate(), 
            WatchUi.SLIDE_UP
        );
        return true;
    }
}