Watermelons are just like other curcurbits Nicky. They produce male and female flowers which normally get pollinated by bees and other insects, but which can easily be manually pollinated by pulling the male flower off the plant, remove the petals and then swab the pistil on all of the female stamens. If it works, you will notice the small fruit behind the female flower continue to grow over the next few days rather than shriveling up and dying. There's nothing to it.

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John - Zone 6

Sorry to hijjak this thread a teeeny bit...but my question is on the same topic. I have 1 watemelon plant left with what looks like a teeny watermelon, how do I know if its been pollinated and will grow? Its the only one on the vine...

Thanks John... I will cross my fingers... its the only one thats developed at all. The rest didn't take or were destroyed.