After the tendril has turned brown, I like to wait about a week to 10 more days to get it really sweet and tasty.
Besides the cream color underneath [usually works] a ripe melon has ceased growing and tends to fade a bit in color and may have a slight ribbing. also on melons other than icebox sizes, the melon tends to have a deeper thumping sound rather than a plink-plink sound.

I grew several watermelons this year and waited until both the tendril and the leaf were brown and shriveled to pick and they were perfectly ripe. I can't say that I'm an expert on the subject, though, but that's just what I did and it worked. Maybe some of the more experienced gardeners can tell if its okay to go ahead and pick it.

Another thing......this will work to some extent on home grown melons and also to boughten ones and especially it works for the small personal size that is sold near year around. Squeeze the melon a bit. If it is very spongy, it is over ripe. If it is brick hard, it likely is not ripe enough. Just like Goldie Locks, it should be in-between.

Mine this year have tended to be over ripe with a brown tendril. Most years that's worked well, not so much this year.

Since I don't like over ripe, I've had to wing it to some degree. Only one or two were really under ripe when picked before the tendril turned fully brown.

Although my melons are Sugar Babies, I too wait another week after the tendril dries up. During this time I back off the watering so that the sugars can concentrate inside. Mine sit on hay as well and I still have a cream spot turn bright yellow. Also, dull wax look turns to shiny and it's hard to put a fingernail dent into skin.

I have only had one watermelon not good. I purposely picket it a little early to compair taste, texture, and color. Other than that I have never had an overwripe one.

Hope some of this info helps,
Bryan

Most of the watermelon varieties I raise hold [keep] very well before becoming overripe. There are some varieties though that quickly get overripe...Dixielee and Orangeglo to name a couple. I also think that where the temperatures are really high that they ripen up faster too.

I have a watermelon left from last year. It is faded some, but otherwise looks ok......wonder what it is like inside?

Thanks for all the replies. I have no idea when the tendril on this particular watermelon died because I was going by the small leaves. I'm a little concerned as the watermelon is the largest in the patch, and I have already had some smaller (cantaloupe size) watermelons crack open.

The spot on the bottom of this one is baseball size, which makes it hard to tell anything. I did try to put a fingernail in it, and the skin is pretty tough. It has been really hot most of the summer, and now it has cooled off quite a bit. I know the cooling off part probably doesn't do much for growing, but it is nice to cut open a watermelon and have it already cool inside.