Robereto
Pretty good
By far the best campsite in Peniscola. It's a bit expensive, but it's right beside the beach. It has a very nice pool with a bar in the middle, but be aware that it's always full, and if you get there 20 minutes after it opens, you won't be able to find a sun lounger. Some details in terms of the maintenance could be improved a bit, but I recommend it highly. You can book a bungalow if you're staying more than a week, and in high season, it's always full.