I purchased this plant as a seedling, the tag said Watermelon 'Charleston
Gray'. The tag said that they are oblong and grow up to 25lbs each.

Mine have been in the soil since the end of May. The pictures that I'm
attaching are showing leaves, and the actual fruit. The growing habit is
similar to that of a cucumber but I don't believe that these are.

What is this thing? Is it a cucumber? A watermelon? Was it mislabeled?

-M