You can either start by pressing the "Start"-button or by pressing the "Stroke" button. If you count every "Catch" then it makes the most sense to start with the "Stroke"-button meanwhile it is best to Start the clock first if you count the "Finish".
While you are on this site, it wouldn't be a problem if you lose your connection as the whole App works in your (mobile) browser. Once loaded, it will continue to work. This means, if you forgot your stroke watch (or lost it in the lake) - we got you covered!
There is no need to install anything, you can use this tool online for free.