We can get 6 packs of seedlings for 2 bucks at the farmers market, but I'd give seed another shot, you should have time

Grrrr! I feel your pain. Though I don't know for sure, I'm wondering either cat or dog? When you replant, I would cover with deer or bird netting, tacked good around the plants with landscape tacks. That has kept the above-ground critters out of my garden very successfully. I pull it off when the plants get big enough for the critters to leave them alone.

If you don't want to buy new ones, you can achieve the size of your seedling in the picture within about a week when its as warm as this. I've been seeing squirrels doing this around my house. I guess they know there's a nut/seed under there. Ive heard blood meal's smell can keep squirrels away. I am not sure how true it is, I myself have let the neighbors cats/my dogs take care of it. In fact my dog came running up to me with the other day with one hanging from his collar. I'd post the picture, but I think some folks here might get offended as the squirrel didn't make it through the whole ordeal. But he was very proud of his new bling!

Oh and I second Loribee on the cats too. I had this issue this year a couple of times:( If you want to know for sure give it a good whiff. if it smells like cat pee, then you've found your culprit.

Do you have armadillos in your area? Mine dig holes like that all the time.

Dave

squirrels, rats do that. But from digging I suspect squirrels.

The circular shape of the holes suggests skunks digging for worms. Just cover that bed with row cover or tulle until the watermelons start running.

Looks like squirrels to me.

squirrels or chipmunks.

I saw a squirrel out my window digging where we had just sown cucumber and radish seed. I was able to quickly get out there and scare him off, but I expected he would be back. I had some leftover wire fencing and hardware cloth in the garage so I got that and laid it over the area and that has stopped the squirrels from digging. I will have to take it up soon, but I'm hoping they have lost interest by then. I probably will lay some remay over it, if I ever find where I put it. [g]

Looks like rat to me. Watermelon seeds are too small of an incentive for squirrels. Get a cat or two! They are much better than dogs at deterring rodents because they are proactive. I have 3 of them and they spend 90% of their time napping in my garden: squirrels stay at bay, possums also ( except for one that they tolerate on the fence only - not on the ground-) birds do not pick my fruits or vegetables, no rats, no mice = peace of mind. With nectarines, apricots, grapes, plum, pears, tomatoes, cantaloupes, watermelon etc, in my garden, there would be rodents all over the place if it wasn't for them!
If you do not want a cat as a pet, associations are giving "barn cats" they are neutered microchipped and vaccinated, they live in barns/sheds and they do their hunter job. But you need to provide a safe place where they can go when it is too cold or too hot, water, food, vaccines, and vet care.
Mine are well fed and are spoiled pets so they don't "over hunt" and sleep on our beds. They run after pests but stop the chase as soon as the critters are out of the garden. Good balance. Squirrels are staying high in the trees ( I like squirrels as long as they don't eat my fruits) I keep a stepladder in between my tomato plants, the cat lays on the upper stair and the birds do not even think about my tomatoes: problem solved.

Snap Traps. Big ones baited with apple slices and peanut butter. You'll find your critter real fast. lol