It's also a way that researchers say could keep fireworks going into the night.
Watermelons contain an ingredient called citrulline that can trigger production of a compound that helps relax the body's blood vessels when consumed in large quantities.
It's similar to what happens when a man takes Viagra.
Someone would need to eat about six cups of watermelon to get enough citrulline to have an impact.
Details come from Texas A&M scientists.