Exploding Watermelon?!?

After Googling a bit I've found this isn't too unusual, but I've never seen it happen before in my life...

I bought our first watermelon of the season yesterday and was really looking forward to slicing it but things didn't go quite as planned. I set it on the dining room table overnight and today we noticed thick white foam coming out of it!



Something was so not right!
I took it outside and more foam kept oozing out of a tiny fissure in it. We finally decided to hack it open to find out what was causing all the foam. The melon was so full of pressure it almost exploded when the knife hit it.

The flesh was a nice rosy color but the rind looked off. There was a thin layer of the foam on it. After my Google search I found our watermelon was infected by wild yeast! Well, that sounds like what happened anyway.

Now I'm debating if I should try to take a pile of watermelon mush back to the store for a refund ... I'm thinking I'm probably just out of $5.  ; >(

Now I'm a little nervous to buy another melon. How can you tell if it's good or not?