Is it ok for you to see your 15 year old daughter naked?

Depends on you and how you feel about it. If you see her in another way than as your daughter you need to stay away and get help. Families seeing each other naked occasionally is not weird when coming out of the shower etc but to seek her up to see her naked would be weird. Especially if she is not in a position to consent to this. In some countries families sit naked in the sauna or goes skinny dipping and it's not a big deal. Some are nudists where it's more natural to not wear clothes than to wear them.
Not if you are the father.