Hear the surf rolling in and the seagulls calling to each other. Feel the sun on your face and the cool sand between your toes. Smell the sea breeze. Feel the mist from the surf on your face. Notice the ships on the horizon and the rolling sand dunes.
Some people find that a mountain scene or a lush meadow scene works well.
You can take yourself to a place you've never been or recreate an experience out of your past. Find a place that works for you and practice getting there. When you become proficient you can return to it quickly for trips that may only last a minute even while you are taking a test. Describe it . Focus your attention on your anxiety.