In less then 5 minutes, you can walk to a free public beach that is just 1½ blocks away from the Marina. Head south (turn right) on Ocean Ave., and access the 3rd staircase over the sea wall. Please note there are no lifeguards present on this beach.
The Borough of Sea Bright also has a public beach (daily beach badge $8, kids under 12 free.) It's located in the center of the business district (one mile north - 2nd traffic light) with plenty of free parking. For more information visit the Sea Bright Borough Beach website.