So you have to make sure it's not high tide before coming down the beach?

The answer is almost always no. I would say that 90% of the time there is plenty of room to drive on the beach at high tide. There is certainly less room than at low tide. Low tide gives you enough beach for about 10 lanes of traffic where high tide gives you enough beach for about 4 lanes, and the sand is going to be looser. I usually don't worry about the tide when driving. The exeption is if I am going to be towing something behind me like a U-Haul trailer or during the other 10% of the time. The other 10% of the time the tide can come as high as the dune line depending a little on the moon and air pressure and a lot on the wind. When there is a Nor'Easter coming in that's when it is best to time your trips more carefully.