Gastric cancer is the third most common cause of cancer-related death in the world, and it remains difficult to cure in Western countries, primarily because most patients present with advanced disease. In the United States, stomach malignancy is currently the 15th most common cancer.
The condition of the tendrils near the fruit stem is another indicator of when a watermelon is ready to pick. When they are green at the attachment point, the fruit is not yet ripe, but when they start to turn brown and dry, it is harvest time.
Look for a melon that is nice looking, meaning free of dents, bruises, cuts, etc. Check under the melon - if it has a yellow or light bottom, it should be ripe. If its stripes are found all around the melon, pass on it. It's just not ready yet. You may see people at the market tapping on watermelon.