I have never tasted a bitter one either. i have tasted cantaloupe that some spoiled spot leaked a bad taste further into the melon.

Try a good tasting watermelon like Raspa [Willhite Seeds].

Sounds like it may be overly ripe and is beginning to rot.

FYI, I got replies from a couple of folks with seed companies. One suggested the possibility that it was mislabeled and was a bitter melon. I find this unlikely since they don't really look like a Sugar Baby watermelon. Another confirmed the answers here that over ripe melons can taste bitter. Also, a boron deficiency can make the melons bitter.

Thanks for your help.

Sandy

I tasted one today.It tasted bitter than bitter leave

By any chance, you had bitter melon grew in the same spot before? Bitter melon is known to leave "bitter taste" in the soil... just a shot in the dark.