Stay calm and focus on staying afloat, rips will not pull you under they just pull you away from shore. Normally a rip will stop just behind breakings waves. 

Remember, if you get stuck in a rip it’s key to not tire yourself out by swimming against it. Stay calm, float with the current and wait for help to arrive. 

What do do:

1. Float on your back, remain calm and don't panic
2. Raise your arm in the air and call for help
3. Continue to tread water and float while you wait for help
4. If you are a confident swimmer, swim with the rip out to sea to just behind the waves. Then swim left or right to catch a wave back to the sandbank and stand up