Borderless Window Mode
 

To have Cold Waters fin the Borderless Window Mode.
1. Enter in game Option menu
2. Turn off fullscreen mode
3. Go to Cold Waters in steam, right click on it, and select properties
4. Click "Set Launch Options" and type in -popupwindow

When you ALT-TAB or clicking out the game, Dangerous Waters will pause and not minimize.

(This is how we do in in KSP as well)