What should you do if your boat turns over or gets swamped?

There is lots of missing info here. Where are you? what's the depth of water? What is the temperature of the water? What is the sea state? Lots of variables to this question, however there are a few things I automatically think of. Don't panic, try to keep calm, a proper mindset can save you even when odds are NOT in your favor. If the boat capsizes or gets swamped try and stay with the boat as long as possible. Even if that means just holding on to whats left. The boat is a larger target, making you easier to find you by Search and Rescue (SAR) assets. Even if you are wearing a Personal Flotation Device (PFD) if you can get out of the water, then try. Getting out of the water even if the air temp is freezing is better than staying in the water (Think of Jack and Rose, who lived, who dies.) Without more detail this is a good start.