I get that your current concern is specifically coyotes eating your watermelon...but I would look to fence the garden against all predators:
deer,
rabbits, groundhog, squirrels, raccoon, birds, etc. All animals and birds will view your garden as just another spot to forage.
I understand this may be an added expense you had not considered, but I highly recommend creating a solid or electrified barrier system that will safeguard your garden from all manner of predation.
You are looking for something unable to be climbed (raccoon, squirrel bunny etc.) so a barrier such as electrified mesh or (used) metal roofing panels used as fence panels to create a barrier something claws can dig into to climb over.
You are looking for something unable to be jumped (deer, coyote, etc.) mesh, electrified or not that would be at least six-eight feet high.
You are looking for something that cannot be dug under (coyote, rodents, etc.) bury your mesh or fencing at least two feet deep OR bend your fencing at ground level and create a two foot extension along the ground, all around the perimeter so that diggers will hit mesh and not break through.
Often a combination of solid climb and dig proof fencing for the first three feet above ground (metal or electrified) then plain metal or plastic mesh for height will do the job - but remember to use bird netting OVER the garden initially so that your young seedlings are not turned into bird food.