If your inside the sandworm zone you must walk without rythm otherwise one of my sandworms will surface and try to eat you. if you walk without rythm or are near a host 5 or more Grungs you will be fine (vehicals are highly unsafe in the sandworm zone)
If a sandworm is about to eat you, hit it with water and it will die. (note sandworms can only come up once per 8 hours and can only stay up for 8 minutes)