Looks like this time I didn't need to fill in the blanks! There's an episode of Billy and Mandy, "No Body Loves Grim", that starts on the beach. One of the things that happens is Mandy gets dragged by the bottom of her swimsuit by a dog, and we later see the dog has a piece of the swimsuit in its mouth. Clearly this is what we didn't see on TV, which is a shame because this stuff is just good. Plus it's nice to see Mandy get her comeuppance.