Lake Meredith National Recreation Area is governed by Codes of Federal Regulations (CFR) and the park superintendent can "model" these regulations to fit the Park's special needs. Not all parks have water-based recreation, historical structures, or even trees. Each park is unique and has it's own unique set of laws, as well as the laws that apply to every unit, such as "littering".
If you have a question that involves whether what you are doing is legal, or not, then you can look in the Superintendent's Compendium to find your answer. All laws and regulations are made to protect fragile natural and cultural resources. These laws and regulations also protect park visitors so we, and our future generations, may keep coming back to enjoy our National Parks.