Pool lifeguard here.
Remember that you're looking to prevent rescues, not hope for them to occur.
another tip. Make sure you're as ugly looking as possible. If you're cute people will try and drown themselves for your attention. And its always ALWAYS the ugly ones.
Try your best not to be a richard at pool rules. People are going to think you're a richard anyway, but take the nice approach first. Don't side in disputes, be the neutral barrier.
Don't be distracted. EVER. You should take the job seriously and not be looking at your phone for most of your shift.