If there's one place in Florida that fits the description of 'pristine' then this National Seashore is the perfect candidate. You will pay a rather steep price at the entrance - forgot exactly how much it was - but it is totally worth it. If you're a Florida resident, there's an annual pass option.

Just be careful if you are with young family members because there are some nude section at the seashore. Also watch out for turtles crossing the street, so you may want to slow down with your driving. Other than these, just relax and enjoy at the beach that is peerless when it comes to cleanness and devoid of human interference.