Do they need to go to the bathroom? Do they all need gasoline for their cars? Snacks to go home? Are they all overloading the stores on the way out? Do they need to hit an ATM?
THAT'S where all the spread will occur. Especially amongst a bunch of entitled dipshits who also don't believe in wearing masks or washing hands.
Unfortunately the people who feel most comfortable leaving the house are the people who are least likely to take precautions, which seems like a recipe for lots of super spreaders to me.
For everybody who drives to the beach (the vast majority of beachgoers), empirical evidence from California beaches suggests that the answers to all those questions is "yes".
If you want to open the beaches only to those who can walk or bike to them, sure that's probably okay. Now, how do you enforce that?
So, we're back to simply closing the beaches completely because it keeps the idiots at bay and is easy to enforce.