What happens next?

How to save watermelon seeds for planting
Collect watermelon seeds from ripe, healthy watermelons.
They generally ripen 35 to 45 days after the plant blooms.
When the watermelon is ripe, the curly tendril on the vine will dry up and turn brown and the white spot on the bottom of the watermelon will turn yellow.

pick from the following.
A). The watermelon will also lose its shine and become dull-looking. Do not collect seeds from watermelons growing on vines that have wilting, spotted or dying leaves or vines.
B). Poke holes on rounded, narrow, and waxy watermelon leaves. This method only works with real watermelon.
C). Check with your local nursery for ready-to-harvest harvest dates, as the plants are disease-resistant. Purchase watermelon seeds from the nursery.
D). Harvest the watermelon by hand, to stop the seed seeds from becoming shriveled or wilted. Harvest your harvested cucumber seeds one to two weeks after making them, if possible.
A).