Q.carrolinacrosse watermelo
How to save a seed of carrolinacross watermelon

It is possible to save and use watermelon seed next year. The link at the end explains the procedure. You won't get the same plant, however. Your watermelon is a hybrid, meaning it has 2 parent plants. Hybrid seeds are like children; you end up with a genetic mixture and offspring do not exactly match the parent. https://www.gardeningknowhow.com/garden-how-to/propagation/seeds/storing-seeds.htm