We have tried the mustard on watermelon trend, and have some thoughts.
We are thinking that perhaps a “baby step” approach might be best.
Further proof of sweet and savory as a winning combination are this deliciouswatermelon and feta saladandwatermelon with tajin.

Credit: Photo: Caitlin Bensel; Food Stylist: Torie Cox
I was bored one day (as a kid usually is) and I put ketchup on the watermelon.
It was too sweet, so I then tried the mustard and that tang was perfect!
One tester said “I’m glad I tried it, but it won’t be my go-to.”

Credit: Caitlin Bensel
This option is a safe and universally palette-pleasing way to go.
We’ve got some other suggestions for using watermelon that will pique your culinary curiosity!
Pork shoulder steaks are braised in a blend of miso, Sambal sauce, mirin, and watermelons.

Credit: Stephen DeVries; Food Styling: Chelsea Zimmer; Prop Styling: Claire Spollen
The result is sweet, savory, and definitely worth multiple attempts to make it perfect the treatment.
Consider these easy bites to be a part of your summer barbecue, guests or not.

Credit:Antonis Achilleos; Prop Styling: Kay E. Clarke; Food Styling: Torie Cox

Credit: Jennifer Davick