Not a watermelon?

So, since we found this mysterious fruit growing in our planter in the back yard we thought it was a watermelon, but looking at it lately is had the rind of a cantaloupe. It still isn't very big, so we haven't picked it yet, but we'll have to before long as it's supposed to cool down and it might freeze Within the next couple of weeks I think we'll pick it and cut it open and give it a taste :) We are all anxious to see now if anything else will grow there next year. I guess we'll have to wait and see.