Apple Tv's and no internet

Hello, I plan to purchase many apple Tv's for a large boat but when this boat is out at sea it will not have internet. I have been hearing mixed information from people about it's ability to work without internet. I have a large hard drive with movies that I have added over the years and they are on iTunes but I have been told that apple tv's will need internet at times to verify a account. Can anybody tell me if this is true or not I have not seen this at my house but they are always online.

Thank you