It would also help if the video automatically scaled to fill as much of the window as possible. On my screen it was a quarter of the entire screen and everything was really tiny.
I'll look into a good cross-browser auto zoom.
I also had some trouble getting the hang of what I was supposed to do. I'd recommend an interstitial to get people going before the video starts. Maybe something like this?
You are about to watch a recorded video of typical activity at a pool. Help the life guard watch all the swimmers in your half of the pool.
If you see someone who needs help from the life guard, click on them in the video and check the results at the bottom of the video.
Since life guards can't do it (as much as they might wish they could!) don't rewind, pause or click the video while being tested unless you would be ready to blow the whistle, jump in, and swim to someone.