White Jellyfish

I was at Eze sur Mer beach swimming next to the club nautique going out to the platform (a platform put out in the sea during the summer season) I saw a White mushroom shaped Jellyfish with no tendrils or nothing hanging from it, it had no colour and was about 5 to 6 inches across the top. Not the usual Mauve Stinger that is normally in these parts, though it is posted they have nets to keep the jellyfish out.